Electricity: battery or capacitor charging or discharging – Battery or cell discharging – Regulated discharging
Reexamination Certificate
2002-06-14
2003-06-03
Tso, Edward H. (Department: 2838)
Electricity: battery or capacitor charging or discharging
Battery or cell discharging
Regulated discharging
C320S141000
Reexamination Certificate
active
06573688
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a technology for detecting a charge/discharge current flowing through a secondary battery mounted on an electrically-driven vehicle such as an electric vehicle (PEV) and a hybrid vehicle (HEV), an uninterruptible power supply system, a backup power source device, and the like.
2. Related Background Art
Recently, nickel-metal hydride (Ni—MH) batteries mainly have been used as a main power source for driving a motor in an electric vehicle (PEV) and a so-called hybrid vehicle (HEV) provided with an engine and a motor, because of their high energy density (i.e., capable of storing energy compactly) and high output density. In the PEV and HEV, an assembled battery made up of a combination of a plurality of single cells or unit cells is employed so as to supply a sufficient output to the motor.
As for HEVs, in a case where an output from an engine is larger than the power required for driving the vehicle, then the surplus power is used for driving a generator so as to charge a secondary battery. Conversely, in a case where an output from the engine is smaller, then the electrical power from the secondary battery is used for driving the motor so as to compensate a shortage of the power. In the latter case, the secondary battery is discharged. When mounting a secondary battery on a hybrid vehicle or the like, it is required to control such charge/discharge operations so as to maintain the appropriate operating conditions. To this end, it becomes necessary that a residual battery capacity (i.e., State of Charge (SOC)) is estimated and an SOC control is conducted so as to optimize the fuel efficiency of the vehicle.
One of parameters for estimating the SOC of a battery is a charge/discharge current in the battery. Therefore, in order to perform the SOC control securely, it is required to use a current sensor that can detect a charge/discharge current in the battery accurately.
Conventionally, as the current sensor used in the HEV or the like, an insulated type current sensor employing a Hall element has been known generally for the purpose of preventing electric leakage. For example, JP 5(1993)-297026A discloses a current sensor including a Hall element, a core provided with a winding, and an electronic circuit. However, this current sensor has the following problems:
(a) the core is provided with a winding, and many windings are required, which makes miniaturization of the current sensor difficult. Especially in the case of the HEV where a principal current is large and a ratio of a detected current at the side of the electronic circuit should be made relatively small, the number of turns of the wiring becomes large, which further makes the miniaturization difficult and leads to an increase in the cost. On the other hand, a wiring with a smaller wire diameter is used for the purpose of miniaturization, which would lead to a temperature rise and fraying of the wiring. Consequently, the reliability of the current sensor would deteriorate;
(b) an offset error in the detected current due to the temperature characteristics of the Hall element would occur;
(c) a circuit is required for not only at the side of receiving the detected current but also at the side of the current sensor, which doubles the number of the components such as a circuit board and therefore is uneconomical; and
(d) when an electrical wiring to the current sensor has failed, a judgment cannot be made as to whether the situation applies to the case where a current does not flow through the wiring or the case where the wiring is broken.
To cope with the above problem (b), JP10(1998)-177926A discloses a current sensor including not a Hall element but a detection coil, an exciting coil, and a core. However, this current sensor does not solve the above problems (a) and (d).
Then, as an alternative for the insulated type current sensor that requires a core provided with a wiring, a current sensor in a shunt resistor method is known, which detects a current flowing through the shunt resistor as a voltage.
For example, JP11(1999)-308701A discloses a battery indicator for electrically-driven vehicles, including a shunt resistor type current sensor within it, and JP5(1993)-66250A discloses an electricity quantity totaling device that detects a charge/discharge electricity quantity of the secondary battery as a pulse using a current detection resistor (shunt resistor), totals this pulse with a counter to store the result, and indicates a residual battery capacity.
The battery indicator described in the above JP11(1999)-308701A is equipped with a shunt resistor within it, as illustrated in this publication. Generally, a driving output of the HEV or the like is large, and therefore a current flowing through the battery becomes large. With the increase in the current, the amount of heat generated in the shunt resistor increases. Therefore, a design to make the permissible loss acceptable makes the shunt resistor large and makes a wire diameter of an electric wiring to the shunt resistor also large. As a consequence, the battery indicator including the shunt resistor and the electric wiring within it becomes large, which would increase the cost and would cause deterioration in the fuel efficiency because of the increase in the weight of the vehicle.
In addition, since the detected current value is large, the resistance value of the shunt resistor should be rather small in order to detect such a large amount of current as a voltage suitable for processing it in a circuit. Therefore, without an expensive high-precision shunt resistor with superior temperature characteristics, an offset error would occur in the detected current.
Further, in the electrically-driven vehicles, a switching current of an inverter flows through the shunt resistor. This switching current has a large amount of high frequency component, which would become a noise source. Therefore, if the shunt resistor is arranged adjacent to a microcomputer and other electronic circuits, then there is the fear of generating a malfunction in the circuit due to the noise, and the reliability would deteriorate.
The electricity quantity totaling device described in the above JP5(1993)-66250A is mounted on mobile equipment such as a camera-integrated video, a mobile phone, a personal computer, and a word processor, and realizes a function of indicating a residual capacity of a secondary battery. Therefore, in contrast to the secondary batteries mounted on the HEV or the like, the detected current is small, and naturally the shunt resistor is included within the device together with other electronic components. Consequently, this publication does not address the problem in detecting a large amount of current flowing through a secondary battery mounted on the HEV or the like as stated above.
SUMMARY OF THE INVENTION
Therefore, with the foregoing in mind, it is an object of the present invention to provide a battery power source device provided with a system capable of detecting a charge/discharge current flowing through a secondary battery mounted on an electric vehicle, an uninterruptible power supply system, a backup power source device, and the like at low cost, with high reliability, and with high precision.
To fulfill the above-stated object, a battery power source device according to the present invention is a battery power source device to which electrical power is supplied from an assembled battery including a combination of a plurality of single cells or unit cells, each of which is a secondary battery, and includes: a current detection resistor connected to the assembled battery in series; transmission means for transmitting a voltage signal generated across the current detection resistor; and a control device separated from the assembled battery, the current detection resistor, and the transmission means. The control device includes: a discharge current detection unit that receives the voltage signal transmitted via the transmission means and outputs a current signal in proportion to a di
Matsushita Electric - Industrial Co., Ltd.
Merchant & Gould P.C.
Tso Edward H.
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