Fluid-pressure and analogous brake systems – Speed-controlled – Regenerative brakes
Reexamination Certificate
1999-10-28
2001-04-10
Butler, Douglas C. (Department: 3613)
Fluid-pressure and analogous brake systems
Speed-controlled
Regenerative brakes
C188S158000, C303S020000, C318S371000, C318S376000
Reexamination Certificate
active
06213571
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to a control apparatus for an electric vehicle and a method thereof for controlling a dc motor for driving the electric vehicle, and in particular, it relates to a braking control of the electric vehicle.
It is known in order to shorten a transition period of time when switching from a regenerative braking mode to a plugging braking mode in an electric vehicle that immediately after detection of a make-contact of a regenerative contactor, a chopper operation for reverse braking is started. It is disclosed in JPA No. 7-46707 that when switching from a regenerative braking to a plugging braking by reading a contact voltage of a regenerative contactor, a main transistor is caused to be on for a minimum period of time during a delay time until the regenerative contactor is closed, and a make contact of the regenerative contactor is detected on the basis of a contact voltage of the regenerative contactor, then a shift to the plugging brake mode is enabled.
In the steps of the aforementioned prior art, it is inevitable when shifting from regenerative braking to plugging braking to stop its regenerative braking once before execution of a regenerative contactor make-contact control, after execution thereof and during a delay time until the regenerative contactor is closed, a main transistor is switched on for a minimum period of time, then the make-contact of the regenerative contactor is detected. Therefore, during the delay time of several tens ms until make-contact of the regenerative contactor, because the main transistor is switched on for the minimum period of time, almost no current conduction state (if any, for a very limited period of time) exists in the motor. During this period of time of no current conduction states in the motor, no braking torque is generated thereby allowing the vehicle to cruise. This period of time without generation of braking torque during transition from regenerative braking to plugging braking is felt by the driver as a switching lag time to deteriorate the feeling during switching therebetween.
Further, although description of detection of the contact voltage of the regenerative contactor is given in the prior art, no consideration is given to a case when the contact voltage of the regenerative contactor cannot be detected due to a failure of wiring or the like.
SUMMARY OF THE INVENTION
An object of the invention is to provide a control apparatus for an electric vehicle and a method therefor, which ensures an improved feeling to be obtained during switching from the regenerative braking to plugging braking by controlling such that switching therebetween is executed while maintaining a condition for its braking torque to sustain without a drop.
Another object of the invention is to provide a control apparatus for an electric vehicle and a method therefor, which ensures operation of the control apparatus for electric vehicle to be maintained even if a contact voltage of the regenerative contactor cannot be detected due to failure of its wiring or the like.
Still another object of the invention is to provide a control apparatus for an electric vehicle and a method therefor, which minimizes a rush current at making contact of the regenerative contactor, a shock of switching therebetween and a damage of contacts of the regenerative contactor.
An aspect of the features of the invention is realized by provision of a control apparatus for an electric vehicle which is comprised of: a dc motor; a field switch unit for interchanging connection of the dc motor so as to interchange a direction of excitation of fields; a dc power source for supplying power to the dc motor; a switching unit for controlling power supplied from the dc power source and a current to flow through the dc motor; a regenerative contactor interconnected between the dc power source and an armature of the dc motor; and a control unit for controlling operation of the switching unit and the regenerative contactor such that the dc motor of the control apparatus for electric vehicle is operated in either mode of powering, regenerative braking or plugging braking, wherein when switching the dc motor from the regenerative braking mode to the plugging braking mode, a rake-contact of the regenerative contactor is detected on the basis of a contact voltage of the regenerative contactor which is a voltage detected between the regenerative contactor and the armature of the motor, and upon detection of the make-contact thereof, operation of the switching unit is stopped, then the mode shifts to the plugging braking.
Another aspect of the features of the invention is realized by provision of a control apparatus for electric vehicle, which is comprised of: a dc motor; a field switch unit for interchanging connection of field windings of the dc motor to interchange a direction of excitation of fields; a dc power source for supplying power to the dc motor.; a switching unit having a switching element for switching power supplied from the dc power source and controlling a current to flow through the dc motor; a regenerative contactor interconnected between a plus terminal of the dc power source and an armature of the dc motor; a control unit for controlling operation of the switching unit and the regenerative contactor, said control unit is provided with an arithmetic unit which produces a drive signal for driving the switching unit and also a drive permission signal, here, a logical product of the drive signal and the drive permission signal is taken to output a drive signal to drive the switching unit such that the dc motor is controlled to operate in the powering, regenerative braking and plugging braking modes, wherein a contact voltage of the regenerative contactor which is detected between the regenerative contactor and the armature of the motor is entered to the arithmetic unit, closure of the regenerative contactor is detected on the basis of the contact voltage detected and entered, and when the dc motor is to be switched from the regenerative braking to plugging braking, a make-contact procedure for closing the regenerative contactor is executed while continuing the regenerative braking even in a delay time until the closure of the regenerative contactor, and upon detection of the closure of the regenerative contactor, the operation of the switching unit is stopped faster than a switching cycle of the regenerative braking thereby allowing for a transition to the plugging braking.
Preferably, detection of the contact voltage of the regenerative contactor according to the invention is carried out in a period of time which starts from where a condition is established for stopping the regenerative braking that the current conduction ratio of the switching device under regenerative braking becomes larger than its threshold value and that the current of the motor under regenerative braking becomes lower than its threshold value, and which ends upon detection of the closure of the regenerative contactor. Further, preferably, the detection of the contact voltage of the regenerative contactor according to the invention is carried out in a cycle faster than a switching cycle of the switching device under the regenerative braking, and upon detection of the closure of the regenerative contactor, by operation of the drive permission signal from the arithmetic unit, the switching unit is stopped its operation faster than the switching cycle of the switching device under regenerative braking.
Preferably, according to the invention, switching of the control modes from the regenerative braking to the plugging braking is done in such a manner that delay times for making-contact of the regenerative contactor are pre-stored in memory with a voltage of the dc power source as its parameter, a time from the start of the make-contact control for the regenerative contactor is measured and compared with a delay time for making-contact of the regenerative contactor based on the voltage of the dc power source, and if a contact voltage of the regenerative contactor i
Kaminaga Minoru
Maehara Kenichi
Takahashi Nobuyoshi
Yamada Hiroyuki
Butler Douglas C.
Evenson, McKeown, Edwards & Lenahan P.L.L.C.
Hitachi , Ltd.
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