Prime-mover dynamo plants – Electric control – Engine control
Reexamination Certificate
2000-09-21
2003-04-29
Ponomarenko, Nicholas (Department: 2834)
Prime-mover dynamo plants
Electric control
Engine control
C180S065510
Reexamination Certificate
active
06555928
ABSTRACT:
RELATED APPLICATIONS
The present application is based on and claims priority to Japanese Patent Application No. 11-267319, filed Sep. 21, 1999, which is hereby expressly incorporated by reference.
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention generally relates to power source control methods for electric vehicles. More particularly, the present invention relates to power source control methods for hybrid-driven vehicles having fuel cells and secondary batteries.
2. Related Art
Electric vehicles, such as hybrid type electric vehicles, have been developed to reduce pollution output from vehicles. The hybrid vehicles generally feature an electric motor that propels the vehicle and two types of energy supply. One of the two types of energy supply can be a battery, such as a lead battery, that is capable of charging and that is capable of supplying electric power to the electric motor in quick response to load changes. The other of the two types of energy supply can be a fuel cell that is adapted to use easily-supplied fuel and that has low pollution output.
It should be mentioned that at least two types of fuel cells have been developed for these hybrid vehicles. One type of fuel cell uses hydrogen gas that is held in a hydrogen gas reservoir as fuel. The other type of fuel cell uses hydrogen gas that is generated in a reformer, such as by combusting methanol, methane or butane, which serves as the primary fuel.
In hybrid vehicles, especially in smaller vehicles such as motorized bicycles, load variation (i.e., the required load due to manipulation of an accelerator or due to changes in the external load resulting from changes in slope or other irregularities in the road) at the motor is substantial. Accordingly, quick response to fluctuations in load is desired.
The large load variation and the desire for quick response presents a dilemma. The fuel cells, if using pure hydrogen in the hydrogen reservoir, suffer from delayed response due to inertia of the hydrogen gas flow (i.e., pulses in the short-time variation of the hydrogen gas flow). The pure hydrogen fuel cells also suffer from unstable output. The fuel cells, if using reformed hydrogen, cannot increase the output of the electric motor immediately following starting or after other sudden load increases because of poor response within the reformer. Thus, the desired quick response power characteristics fail to be achieved consistently.
Accordingly, at the time of sudden load increase, increased electric power has been supplied by a hybrid system with a battery to cope with the delayed response of the fuel cell. This battery supplied power increase must be sustained until the fuel cell power output rises to the challenge. During this period of time, the load on the battery can exceed a threshold level and the battery charge can fall abruptly. The abrupt decrease in battery charge can result in decreased travel distance or shorter battery life.
SUMMARY OF THE INVENTION
In view of the foregoing, one aspect of the present invention provides a power source control method for a hybrid vehicle. The method preferably is capable of coping with load change by making proper use of two disparate power sources according to the operating characteristics of each. By accounting for the operating characteristics of the battery and the fuel cell, more stable operation of the vehicle results. In addition, the method advantageously reduces capacity shortening and deterioration of the battery.
Another aspect of the present invention involves a power source control method for a hybrid-driven mobile body comprising a motor type power system for travelling, a fuel cell and a battery as power sources. The power sources supply electric power in response to loads on the power system, wherein to a varying load, electric power corresponding to a base load portion at a given level and with a substantially small variation is supplied from the fuel cell and electric power corresponding to a varying load portion is supplied from the battery.
According to this arrangement, the fuel cell constantly bears a load of a given level as a base load portion, and the battery bears a varying load portion exceeding the base load portion. Therefore, electric power is supplied from the fuel cell which is substantially constant or varies slowly according to the operating mode, while electric power is supplied from the battery for the varying load portion that exceeds the base load portion, thereby decreasing burden of the battery, reducing abrupt capacity drop or deterioration of the battery, and providing more stable running by distributing the whole load more efficiently between the fuel cell and the battery.
In a preferred arrangement, the base load portion is increased when the capacity of the battery is smaller than a specified value, and the base load portion is decreased when the capacity is larger than a specified value.
According to this arrangement, the remaining capacity of the battery is metered. If the remaining capacity is smaller than a specified value, the base load portion is raised to increase power supply by the fuel cell beyond the actual load to charge the battery. If the remaining capacity is larger than a specified value, the base load portion is lowered to decrease power supply by the fuel cell and to increase the battery load share so as to discharge the battery. One result of this aspect is that the capacity of the battery is maintained in a proper condition.
In another preferred arrangement, electric power is supplied continuously from the fuel cell after the vehicle is stopped. According to this arrangement, power generation by the fuel cell continues when the vehicle temporarily stops running. The power generated during this period charges the battery.
One aspect of the present invention involves a method for controlling an electric vehicle having a first power source and a second power source. The method comprises sensing a load level, calculating a base load, supplying the base load from the first power source and supplying a remainder of the sensed load level from the second power source.
Another aspect of the present invention involves an electric vehicle comprising a frame with at least one driven wheel rotatably connected to the frame. A motor unit is supported by the frame and is drivingly connected to the at least one driven wheel. A control unit is adapted to communicate with the motor unit. Power is supplied to the motor unit from a first power source and a second power source. The control unit is adapted to calculate a base load that is supplied by the first power source. The control unit is adapted to sense a varying load demand and to compensate for differences between the base load and the varying load with power supplied by the second power source.
REFERENCES:
patent: 4962462 (1990-10-01), Fekete
patent: 5631532 (1997-05-01), Azuma et al.
patent: 5656921 (1997-08-01), Farrall
patent: 6175217 (2001-01-01), Da Ponte et al.
Kuranishi Masahisa
Mizuno Yutaka
Saitou Mikio
Yamada Toshiaki
Knobbe Martens Olson & Bear LLP
Ponomarenko Nicholas
Yamaha Hatsudoki Kabushiki Kaisha
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