Power source unit for transferring energy between power...

Details Power source unit for transferring energy between power... Power source unit for transferring energy between power...

1998-11-05

2001-07-24

Wong, Peter S. (Department: 2838)

Electricity: power supply or regulation systems

In shunt with source or load

C363S056070, C363S097000

Reexamination Certificate

active

06265853

ABSTRACT:

DETAILED DESCRIPTION
1. Field of the Invention
The present invention relates to a power source unit for effectively transferring energy between the first and the second power sources and an electric vehicle loaded therewith, and more particularly, to a power source unit comprising first and second power sources and an insulation type power transfer circuit such as a current control circuit, etc.
2. Prior Art
It is generally known that the use of cells under a rapidly changing loading condition makes a capacity thereof smaller and a duration of life shorter compared with a constant loading condition. Cells applied to an electric vehicle, for example, exhibit such undesirable phenomena.
Radical, rapid and frequent changes in the load condition of cells are seldom observed in such equipment and devices as portable personal computers, e.g., lap top computers, or portable audio systems, e.g., handy cassette recorder, etc.
In the case of an electric vehicle, however, loading to motors, etc. (or motor load) changes radically, rapidly and frequently when the vehicle starts, accelerates, brakes or goes up a slope. Such a change in motor load directly affects the loading condition of cells, which causes a decrease in the capacity and shortening of the duration of life more remarkably than those cells used under a constant loading condition.
A power source unit for conventional electric vehicles is generally designed to meet the above mentioned radical, rapid and frequent change in motor load even though the capacity and the duration of life of cells are sacrificed to a certain extent. On the other hand, it is also tried to develop a power source unit for electric vehicles sufficient to increase the capacity and the duration of life of cells.
For example, a change in a loading condition of a cell as a main power source has been conventionally controlled to keep constant to the utmost by means of a power source unit which comprises a combination of the main power source and a cell or condenser of high capacity as a sub power source, thereby charging the above mentioned radical, rapid and frequent change in the motor load to the sub power source.
FIG. 4
shows a conventional power source unit for electric vehicles. The power source unit
5
comprises a main power source
51
including a cell and a sub power source
52
including a cell or condenser. The main power source
51
and a sub power source
52
are connected in parallel (in
FIG. 4
, a condenser is used as the sub power source for convenience). Energy is supplied from the power source unit
5
to a motor unit
6
comprising an inverter
61
and a vehicle driving motor
62
.
In the power source unit
5
, a terminal voltage of the main and sub power sources
51
and
52
is the same. As a partial current charge ratio is spontaneously determined by an inverse ratio of respective internal resistance (R
1
and R
2
) it is limited to control the change in the loading condition of the main power source within a certain level of range.
In order to prevent the above mentioned inconvenience, it is known that a power source unit
5
comprises a current control circuit
53
consisting of a DC/DC converter which is connected between a main power source
51
and a sub power source
52
, as shown in FIG.
5
. In the power source unit
5
, a current division ratio of the main power source
51
and the sub power source
52
is determined by a current control circuit
53
, thereby the loading condition of the main power source
51
being limited within a certain region.
When energy transfer is performed between the main power source
51
and the sub power source
52
in the power source unit
5
shown in
FIG. 5
, however, efficiency of energy transfer in the current control circuit
53
directly affects that of the electric power source unit as a whole because energy inevitably passes through the circuit
53
. Consequently, a merit of securing a sufficient capacity of the main power source by arranging the sub power source is inversely decreased or canceled due to the current control circuit
53
when energy loss therein is significant.
As matter of course, it is possible to increase the overall efficiency of the power source unit by means of a current control circuit of higher energy transfer efficiency, but such a circuit is expensive and raises the production cost of electric vehicles.
In the above mentioned examples, a cell is used as the main power source
51
in the power source unit, while a fuel cell or an engine generator is employed as the main source in the case of a so-called hybrid electric vehicle. In a normal internal combustion type vehicle driven by a gasoline engine, the engine efficiency decreases accompanying an increase in toxic exhaust gas under a heavily loaded condition such as when the vehicle starts, accelerates, brakes goes up a slope. On the other hand, in the above mentioned hybrid vehicle in which the main power source is, for example, an engine generator, it is possible to drive the generator most efficiently under a constant condition with exhausting a lesser amount of toxic gas. That is to say, the engine generator as the main power source is most efficiently driven under a constant condition with exhausting lesser amount of toxic gas to charge the sub power source, and the thus charged energy therein is used to drive a vehicle driving motor under the considerably loaded condition.
As shown in
FIG. 6
, in such a power source unit
7
of a hybrid electric vehicle, a current control circuit
73
is arranged between a main power source (i.e., engine generator)
71
and a sub power source (in this example, shown as a cell)
72
. Here again, in the power source unit
7
, when energy transfer is performed between the main power source
71
and the sub power source
72
, the efficiency of energy transfer in the current control circuit
73
directly affects the overall efficiency of the power source unit because all energies pass through the current control circuit
73
.
Consequently, a merit of improving specific fuel consumption and decreasing the toxic exhaust gas by driving the vehicle under a constant condition is inversely decreased or canceled due to the current control circuit
73
when energy loss therein is significant.
OBJECT OF THE INVENTION
It is an object of the present invention to provide a power source unit comprising first and second power sources and a insulation type power transfer circuit having two input terminals and two output terminals in which energy transfer is effectively performed between the first and the second power sources, and an electric vehicle loaded therewith.
SUMMARY OF THE INVENTION
The present invention has been made based on the recognition of that, in a power source unit comprising first and second power sources and an insulation type power transfer circuit having two input terminals and two output terminals, when energy is transferred from the first power source to the second power source, if it is possible to transfer only a part of energy through an insulated type power transfer circuit, energy loss in the power transfer circuit can be reduced.
A power source unit according to the present invention comprises a first power source, an insulated type power transfer circuit having two input terminals and two output terminals, and a parallel circuit including a second power source and a load unit. The first power source is connected between the two input terminals of the insulated type power transfer circuit. One of terminals of the first power source is connected to the first output terminal of the insulated type power transfer circuit. The parallel circuit is connected between the second output terminal of the insulated type power transfer circuit and the second terminal of the first power source. In this power source unit, energy transfer is performed between the first power source and the parallel circuit.
The first power source may be an generator (generally, DC generator) or a fuel cell, or a galvanic cell (hereinafter simply referred to as a cell) , while the second power

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