Data processing: vehicles – navigation – and relative location – Vehicle control – guidance – operation – or indication – Electric vehicle
Reexamination Certificate
2002-04-03
2003-10-21
Cuchlinski, Jr., William A. (Department: 3661)
Data processing: vehicles, navigation, and relative location
Vehicle control, guidance, operation, or indication
Electric vehicle
C701S105000, C180S065100, C180S065230
Reexamination Certificate
active
06636788
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an apparatus for controlling an electric motor and an apparatus for controlling a hybrid vehicle.
2. Description of the Related Art
Electric vehicles and hybrid vehicles which incorporate electric motors for generating propulsive forces for the vehicles operate selectively in power and regenerative modes for the electric motors depending on the operating state (the accelerator pedal operation, the vehicle speed, etc.) of the vehicles. Generally, a torque command value (a command value of the power torque or regenerative torque) for the electric motor is generated depending on the operating state of the vehicle, and an output torque of the electric motor is controlled depending on the generated torque command value. Various control processes including a so-called d-q vector control process are known in the art for controlling the output torque of the electric motor depending on the torque command value.
Electric motors mounted on electric vehicles and hybrid vehicles are required to produce a wide range of output torques in view of their application, and are often needed to produce an output torque in excess of the rated torque at which the electric motors are capable of continuous operation without fail. Therefore, the electric motors are frequently operated while generating a relatively large amount of heat with a large current passing therethrough, and hence are required to prevent themselves from being overheated. According to a known solution, as disclosed in Japanese laid-open patent publications Nos. 11-27806 and 2000-32602, the temperature of an electric motor is detected by a temperature sensor, and when the detected temperature exceeds a predetermined temperature, the output torque of the electric motor is forcibly limited.
However, the conventional arrangement which uses the temperature sensor to detect the temperature of an electric motor is highly costly because it requires the temperature sensor itself and parts by which the temperature sensor is installed on the electric motor. Furthermore, a plurality of temperature sensors need to be actually used for continued operation in the event of a temperature sensor failure. As a result, the cost of the entire system is higher, and it is hard to keep an installation space for the temperature sensors.
SUMMARY OF THE INVENTION
It is therefore an object of the present invention to provide an apparatus for controlling an electric motor to prevent the electric motor from being overheated with an inexpensive simple means without the need for temperature sensors.
Another object of the present invention to provide an apparatus for controlling a hybrid vehicle to prevent an electric motor in the hybrid vehicle from being overheated with an inexpensive simple means.
The inventors have found that while an electric motor is operating with a normal output torque, e.g., an output torque smaller than a rated torque, the temperature of the electric motor generally does not become excessively high, and the steady temperature of the electric motor during such an operating state is substantially constant. For preventing the electric motor from being overheated, it is considered sufficient to be able to recognize temperature changes of the electric motor basically in a situation where the output torque of the electric motor is relatively large.
A temperature change of the electric motor within a sufficiently short period of time (an instantaneous temperature change), or particularly a temperature change upon a temperature increase from the steady temperature of the electric motor, can be inferred using data of a torque command value for the electric motor and data of an average of torque command values. Since a current flowing through the armature of the electric motor is basically proportional to the torque command value, the torque command value is closely related to the amount of heat (Joule heat) generated by the electric motor which is mainly responsible for the temperature increase of the electric motor. The average of torque command values is closely related to the tendency of the temperature change of the electric motor (the tendency for the temperature change of the electric motor to increase or decrease). Therefore, it is possible to appropriately infer the temperature change of the electric motor using the data of the torque command value and the data of the average of torque command values.
To achieve the above objects, there is provided in accordance with the present invention an apparatus for controlling an electric motor depending on a torque command value, comprising inference means for sequentially calculating an inferred value of a temperature change of the electric motor in each cycle time using at least data representing the torque command value and data representing an average of torque command values, integrating means for sequentially integrating the inferred value of the temperature change of the electric motor to calculate an accumulated temperature change, and output limiting means for limiting the output of the electric motor when the accumulated temperature change exceeds a predetermined output limiting threshold.
According to the present invention, there is also provided an apparatus for controlling a hybrid vehicle having an engine for generating a propulsive force for the hybrid vehicle, an electric motor coupled to an output shaft of the engine for selectively generating an assistive propulsive force for the hybrid vehicle in a power mode and generating electric energy using the kinetic energy of the hybrid vehicle as an energy source in a regenerative mode, depending on the operating state of the hybrid vehicle, and an electric energy storage device as a power supply for the electric motor in the power mode, the arrangement being such that a torque command value for the electric motor is generated depending on the operating state of the hybrid vehicle, and the electric motor is controlled depending on the torque command value, the apparatus having the inference means, the integrating means, and the output limiting means described above in the apparatus for controlling the electric motor.
With the apparatus for controlling the electric motor and the apparatus for controlling the hybrid vehicle according to the present invention, using at least the data representing the torque command value and the data representing the average of torque command values, it is possible to appropriately infer a temperature change of the electric motor in each cycle time. By integrating the inferred value of the temperature change with the integrating means, an accumulated temperature change from an arbitrary temperature of the electric motor can sequentially be recognized. When the accumulated temperature change exceeds the output limiting threshold, the output of the electric motor is limited by the output limiting means thereby to prevent the electric motor from being overheated. The accumulated temperature change can be determined by a processing operation of a microcomputer or the like without the need for sensors such as temperature sensors.
According to the present invention, therefore, the electric motor is prevented from being overheated with an inexpensive arrangement without the need for sensors such as temperature sensors.
With the apparatus for controlling the electric motor and the apparatus for controlling the hybrid vehicle according to the present invention, various algorithms may be employed to determine the inferred value of the temperature change. For example, the inference means may comprise fuzzy inference means for sequentially calculating an inferred value of a temperature change of the electric motor according to a fuzzy inference operation using at least the data representing the torque command value and the data representing an average of torque command values as input parameters.
According to the inventors' finding, when the data representing the torque command value and the data representing the average of to
Shirasaka Takuya
Tamagawa Yutaka
Arent Fox Kintner & Plotkin & Kahn, PLLC
Hernandez Olga
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