The disclosure generally relates to power usage and temperature control of hybrid electric vehicle batteries.
Typical parallel hybrid electric vehicles include an internal combustion engine, an electrical machine, and a battery. Parallel hybrid electric vehicles typically operate using the electric machine and/or the internal combustion engine as prime movers to propel the vehicle. That is, torque may be provided to the vehicle wheels using only the electrical machine, only the engine, or using some combination of torque from both prime movers. Generally, the electrical machine will work as a motor or generator during the period of vehicle acceleration or deceleration, respectively. An inverter may be operably positioned between the electrical machine and the battery to implement the electrical DC or AC power conversion between the electrical machine and the battery.
In a hybrid mode, both the electrical machine and the engine may provide torque to the driven wheels of the vehicle for propulsion. During acceleration or electric only operation, the electrical machine will function as a motor to help propel the vehicle, and the battery will discharge to provide electrical power to drive the motor. During deceleration operation, the electrical machine will function as a generator to charge the battery by absorbing the deceleration mechanical energy.
Because of frequent stop-and-go or acceleration-and-deceleration vehicle operation, the battery will be charged and discharged frequently in a cycling operation. Such cycling operation typically results in heat generation by the battery. The longer the discharging/charging period or the greater the charging/discharging current, the more heat the battery will generate, thus resulting in higher battery temperatures which may impact battery life significantly.
A de-rating of the battery may be used where the battery temperature is monitored and the power supplied by the battery is limited when the battery temperature exceeds a preselected level (or the battery power may be lowered proportionally as the temperature increases). However, this de-rating may not prevent the battery from exceeding an undesirable temperature, and may result in operating the battery unnecessarily at a de-rated capacity. Further, to increase the fuel efficiency of a hybrid vehicle, the battery should operate at the highest capacity possible, and to improve the hybrid battery life, the battery should operate below the desirable temperature.
Referring now to the drawings, illustrative embodiments are shown in detail. Although the drawings represent some embodiments, the drawings are not necessarily to scale and certain features may be exaggerated, removed, or partially sectioned to better illustrate and explain the present invention. Further, the embodiments set forth herein are exemplary and are not intended to be exhaustive or otherwise limit or restrict the claims to the precise forms and configurations shown in the drawings and disclosed in the following detailed description.
Controller 32 may be electronically and microprocessor-controlled and may provide output information to an electronic data link DL, preferably conforming to the industry standard SAE J1939 or a comparable protocol. A data link, conforming to the SAE J1939 protocol or a comparable protocol, transmits information by which information associated with the prime mover and related components may be interpreted and acted upon. Controller 32 may be a single controller or one of a series of interconnected controllers. Although not shown, controller 32 may be of general construction having a central processing unit (CPU), various co-processors, a read only memory (ROM), a random access memory (RAM), an input for selectively receiving data via a data link from various vehicle components including the prime movers and related components, an output for selectively transmitting command output signals, and a bi-directional bus interconnecting the components.
The controller 32 detects the current flowing through the battery 30, as described in greater detail below. Specifically, the controller 32 may control a Battery Management System (BMS) 40 that detects battery parameters and controls the usage of components within the system 20. BMS 40 is connected to controller 32 such as by a CAN link. Alternatively, the BMS may include at least a portion of the controller 32. The current may be measured either directly, such as by controller 32, or indirectly. Indirect measurements of the current may be obtained by measuring a voltage drop across a path carrying a current where the resistance is known or measured, by measuring a magnetic field about a current carrying wire, or by other known methodologies.
The engine 22 includes an output engine shaft 50; the motor-generator 26 includes a motor input shaft 52; and the transmission 28 includes a transmission input shaft 54 and at least one transmission output shaft 56. The clutch assembly 24 selectively couples the engine 22 to the motor-generator 26. The system 20 may also include a transmission input shaft speed sensor 60. Generally, the motor input shaft 52 is coupled for rotation with the transmission input shaft 54 such that the transmission input shaft speed sensor 60 will detect movement of the motor input shaft 52.
Also in the illustrative arrangement of
As used herein, the Root Mean Square (RMS) current flowing through the battery is calculated by the equation:
Where
I(t) represents the time-varying battery current, and
T1 and T2 represent the beginning and ending times of a rolling, fixed-duration sampling period. In one example, the sampling period is 180 seconds.
The heat generated by the battery during the charging and discharging operations of the battery can be attributed to the internal impedance of the battery, and the heat dissipation is proportional to the average power of the battery, as shown below:
Pavg=(IRMS)2R Equation 2
Where R represents the internal impedance of the battery.
During the charging and discharging operations of the battery, the increase in the battery temperature is highly related to battery power loss, which may be represented as:
ΔT∝Pavg Equation 3
Where ΔT represents the increase in the battery temperature.
In one exemplary embodiment of operating the system 20, the BMS 40 detects the current, calculates the I2T accumulation value over a predetermined period of time, and broadcasts the I2T accumulation value. In one example, the period of time is 180 seconds, although the length of the period of time can be varied. The time period is selected under the considerations of thermal limitations of battery cells and cell connection, and through experimentation.
In the example presented, the I2T accumulation value is desired to never exceed 350,000. This I2T accumulation value limit is selected through experimentation, in an effort to balance performance and cycle life of the battery. Therefore, it is desired that the controller 32 will operate the system 20 and manage the battery 30 such that the I2T accumulation value will not exceed 350,000, while still attempting to attain the best performance.
In the example of
Further, in the example presented, the EV Torque operational mode may be utilized when the BTC value is 0.30 to 1.0, and the controller 32 may not permit the system 20 from operating in the EV Torque operational mode when the BTC value is less than 0.30. De-rating of the EV Torque operational mode may occur when the BTC value is between about 0.4 and 0.3. Also, the SplitRegen, SplitBoost, and MaxBoost operational modes, the least important operational modes, may be utilized when the BTC value is 0.50 to 1.0, and the controller 32 may not permit the system 20 from operating in the SplitRegen, SplitBoost, and MaxBoost operational modes when the BTC value is less than 0.50. De-rating of the SplitRegen, SplitBoost and MaxBoost operational modes may occur when the BTC value is between 0.9 and 0.5. Accordingly, the controller 32 may prevent the hybrid powertrain system 20 from operating in at least one of the plurality of operating modes in response to the determined BTC value.
As shown in
Although a generally linear decrease in the performance capacity of the MaxBoost and the Regen braking operational modes is illustrated, the graphs of
While the powertrain system 20 is illustrated in one exemplary approach, the novel aspects contained herein may be used with any powertrain system, such as parallel hybrid systems, series hybrid systems and combined hybrid systems.
Further the illustration of
The preceding description has been presented only to illustrate and describe exemplary embodiments of the methods and systems of the present invention. It is not intended to be exhaustive or to limit the invention to any precise form disclosed. It will be understood by those skilled in the art that various changes may be made and equivalents may be substituted for elements thereof without departing from the scope of the invention. In addition, many modifications may be made to adapt a particular situation or material to the teachings of the invention without departing from the essential scope. Therefore, it is intended that the invention not be limited to the particular embodiment disclosed as the best mode contemplated for carrying out this invention, but that the invention will include all embodiments falling within the scope of the claims. The invention may be practiced otherwise than is specifically explained and illustrated without departing from its spirit or scope. The scope of the invention is limited solely by the following claims.
Number | Name | Date | Kind |
---|---|---|---|
5540202 | Cullen et al. | Jul 1996 | A |
5617836 | Cullen et al. | Apr 1997 | A |
6112724 | Kotwicki et al. | Sep 2000 | A |
6232744 | Kawai et al. | May 2001 | B1 |
6727670 | Grabowski et al. | Apr 2004 | B1 |
6870336 | Murakami et al. | Mar 2005 | B2 |
6898505 | Kadota et al. | May 2005 | B2 |
7216729 | Syed et al. | May 2007 | B2 |
7267191 | Xu et al. | Sep 2007 | B2 |
7368886 | Hsieh et al. | May 2008 | B2 |
7420292 | Busdiecker et al. | Sep 2008 | B2 |
7639018 | Zettel et al. | Dec 2009 | B2 |
7688074 | Cox et al. | Mar 2010 | B2 |
7869911 | Yamaguchi | Jan 2011 | B2 |
20040162683 | Verbrugge et al. | Aug 2004 | A1 |
20070284162 | Zettel et al. | Dec 2007 | A1 |
Number | Date | Country | |
---|---|---|---|
20110048823 A1 | Mar 2011 | US |