Electrical transmission or interconnection systems – Vehicle mounted systems – Automobile
Reexamination Certificate
1999-06-29
2001-11-20
Ballato, Josie (Department: 2836)
Electrical transmission or interconnection systems
Vehicle mounted systems
Automobile
C361S031000
Reexamination Certificate
active
06320275
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to a power-feed control apparatus provided in a vehicle for controlling turn-on or off operations of electrical loads such as lamps, motors, and so on, using power semiconductor elements with a protection function to detect an anomaly in a circuit including each load and to interrupt the power-feed to the load in the circuit, and especially relates to a power-feed control apparatus suitable for a vehicle in which electrical loads are incorporated being controlled by a network system using a serial-transmission line.
In a general conventional method, a current flow fed to a load is detected, and if the current flow excessively increases, the current flow is interrupted. This method is implemented with MOS-FETs in techniques disclosed in Japanese Patent Application Laid-Opens Sho. 61-2611920, Sho. 62-11916, Sho. 62-143450, and Sho. 63-87128.
Furthermore, a technique disclosed in Japanese Patent Application Laid-Open Hei. 8-303018 permits a large starting current of a load such as a lamp, and interrupts a power-feed to a load if a short-circuit anomaly is detected at the load.
The above conventional techniques cannot deal with an anomalous consumption of energy in a battery due to a rare short-circuit (incomplete short-circuit) in a load, a locking anomaly of a motor due to an extraneous part inserted into the motor, an anomaly (generation of heat, inflammation, etc.) of the whole control system due to accumulation of heat slightly and continuously generated in power lines, and so on.
That is, if a power element with only one protection function based on current or temperature is designed so that the power element does not interrupt a power-feed to a load connected to the power element during the initial period with a large starting current flow, a comparatively small and anomalous change of current flowing in the power element in a steady-state cannot be detected and dealt with. Further, in a power-feed control system in which an anomaly in temperature or current is detected and the interruption of power-feed is performed for each load, the composition of the control system becomes complicated and expensive. In a method in which a current detection resistor is serially connected to a load, the power loss at the current detection resistor is large, which increases the waste heat generation.
SUMMARY OF THE INVENTION
The present invention has been achieved in consideration of the above-described problems, and is aimed at realizing a protective function for a power-feed control apparatus for a vehicle, which does not respond to a large starting current just after a load is turned on via a power element, and can sensitively detect an anomalous change of current flowing in the power element in a steady state, and is further aimed at cheaply providing a power-feed control apparatus with the above protective function, which can decrease power consumption.
In order to attain the above object, the present invention provides a means for switching a protective function between one for the starting period and one for the steady state of current flowing in a power element in a power-feed control apparatus. Further, the present invention provides another means for monitoring current flowing in the power element or the temperature of the power element roughly in the starting transient state and precisely in the steady state. Furthermore, the present invention provides a protective circuit for the initial period with a large transient current flow and another protective function for the period with a steady current flow, and uses the latter protective function in the steady state after the initial transient state has lapsed. Moreover, in another means provided by the present invention, the current fed to each power element is serially turned on and off, in which the time width for the turning-off of the power element is much shorter than that of the turning-on of the power element, and it is monitored whether or not the difference between two current flow levels at the turning-on state and the turning-off state of the power element is less than a predetermined reference value.
REFERENCES:
patent: 4532567 (1985-07-01), Kade
patent: 4639609 (1987-01-01), Floyd et al.
patent: 4672278 (1987-06-01), Ingraham et al.
patent: 5231309 (1993-07-01), Soma et al.
patent: 5559375 (1996-09-01), Jo et al.
patent: 5666044 (1997-09-01), Tuozzolo
patent: 5773945 (1998-06-01), Kim et al.
patent: 61-261920 (1986-11-01), None
patent: 62-11916 (1987-01-01), None
patent: 62-143450 (1987-06-01), None
patent: 63-87128 (1988-04-01), None
patent: 10-145205 (1998-05-01), None
patent: WO 96/26570 (1996-08-01), None
Okamoto Kaneyuki
Osaka Ichiro
Saito Hiroyuki
Sakamoto Shin'ichi
Watanabe Mitsuhiko
Ballato Josie
Crowell & Moring LLP
Hitachi , Ltd.
Polk Sharon
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