Data processing: vehicles – navigation – and relative location – Vehicle control – guidance – operation – or indication – Electric vehicle
Reexamination Certificate
2001-10-03
2003-04-15
Chin, Gary (Department: 3661)
Data processing: vehicles, navigation, and relative location
Vehicle control, guidance, operation, or indication
Electric vehicle
C180S065230, C180S065310, C180S065600
Reexamination Certificate
active
06549832
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to a control device for a front and rear wheel drive vehicle and, more particularly, to a control device for a front and rear wheel drive vehicle wherein one of front and rear wheel pairs is driven with an engine and the other one of the front and rear wheel pairs is driven with an electric motor.
BACKGROUND OF THE INVENTION
In recent years, extensive research and development works have been undertaken to provide a front and rear wheel drive vehicle wherein one of front and rear wheel pairs is driven with an engine and the other one of the front and rear wheel pairs is driven with an electric motor. The front and rear wheel drive vehicle is a vehicle which serves as a hybrid vehicle having a low fuel consumption and which serves as a four-wheel drive vehicle having a running stability.
In general, the front and rear wheel drive vehicle includes a battery that stores electric power to be supplied to the electric motor, and an electric power generator that charges the battery. In a case where the electric motor, which drives the wheels, serves as the electric power generator, the electric motor regenerates a portion of the running energy of the vehicle as an electrical energy, i.e., a regenerative power which is charged into the battery. Usually, the electric motor functions to produce regenerative power during a decelerating condition of the vehicle wherein an accelerator pedal is not depressed. However, in an event that a power remaining capacity level of the battery is below a given power remaining capacity level, a forced charging operation is carried out even when the accelerator pedal is depressed. During regenerative operation of the electric motor, also, a brake force is applied to the wheels associated with the electric motor on account of its regenerative operation.
In addition, the front and rear wheel drive vehicle includes a control device which is arranged to set a drive power of the engine and a drive power of the electric motor and controls the engine and the electric motor in respective control modes. For example, the control modes involve a low &mgr;-road running mode for the sake of a running stability at a road with a low frictional coefficient (that will be hereinafter referred to as “&mgr;”), a fuel saving mode for the sake of fuel consumption and a forced charging mode to be executed when the power remaining capacity level of the battery is lowered, based on which the engine and the electric motor are controlled. More particularly, in the low &mgr;-road running mode, a drive power split is carried out in a limited range of power output to be delivered to the road from the respective wheels so as to avoid a slip. In the fuel saving mode, further, the drive power split is carried out so as to attain a high operating efficiency of the engine. In the forced charging mode, also, the drive power of the engine and the amount of electric power to be charged by the electric motor are suitably distributed within a limited range of power output produced by the engine. In this connection, the respective control modes are automatically changed over with the control device and may also be manually changed over by a vehicle driver.
SUMMARY OF THE INVENTION
However, if the lowest power remaining capacity level, which serves as a reference to discriminate the forced charging mode to be changed over, remains at a constant value regardless of the road surface conditions, there are some instances where the low fuel consumption of the hybrid motor is degraded. For example, in a case where, when the atmospheric temperature remains at a normal temperature level, the vehicle is continuously ascending the upward slope with a high &mgr;-road, since the electric motor also drives the wheels, a gradual decrease will arise in the remaining capacity level of the battery. When this occurs, the power remaining capacity level of the battery decreases to a value below the lowest power remaining capacity level, with a resultant changeover into the forced charging mode. But, in usual practice, a continuous downward slope will appear in a case where the vehicle has passed through the continuous upward slope, and the vehicle encounters a continuous descending phase after a continuous ascending movement. Accordingly, in spite of a probability in that the power remaining capacity level of the battery is expected to be increased due to the regenerative power produced during the decelerating condition of the vehicle at the continuous downward slope, the control device tends to execute the forced charging operation during the continuous ascending operation. When this occurs, since the braking force is applied to the wheels associated with the electric motor during the forced charging operation, the engine tends to operate at a lowered fuel saving efficiency to compensate for such a braking force. In a case where the low &mgr;-road is caused to appear due to snow, further, there are many instances where the low &mgr;-road will continue for a long time period. In such a case, since an electric power consumption of the electric motor will remarkably increase on account of driving the vehicle in the low &mgr;-road running mode, it is required for the power remaining capacity level of the battery to be maintained at an increased level as high as possible. In addition, the lower the battery temperature, the lower will be the performance of the battery to supply electric power. To address this issue, it is necessary for the battery to be charged and the temperature of the battery to be increased to a level as high as possible. However, the presence of the lowest power remaining capacity level of the battery maintained at the constant level regardless of the road surface conditions or the battery performance suffers a problem in that it is difficult to charge the battery at a suitable timing.
It is therefore an object of the present invention to provide a control device for a front and rear wheel drive vehicle wherein regenerative power is produced in dependence on road surface conditions and a battery performance for thereby providing an improved fuel consumption.
According to an aspect of the present invention, there is provided a control device for a front and rear wheel drive vehicle wherein one of a front wheel pair and a rear wheel pair is driven with an engine and the other one of said front wheel and rear wheel pairs is driven with an electric motor with electric power output produced by electric storage means, which comprises drive condition detection means for detecting drive conditions of said front and rear wheel drive vehicle, road surface frictional coefficient estimating means for estimating a road surface frictional coefficient, atmospheric temperature detection means for detecting an atmospheric temperature, temperature detection means for detecting a temperature of said electric storage means, motor drive power calculation means for calculating a drive power of said electric motor on the basis of the running condition detected by said drive condition detection means and the road surface frictional coefficient estimated by said road surface frictional coefficient estimating means, and control mode changeover means for changing over control modes during calculation of the drive power of said electric motor on the basis of the atmospheric temperature detected by said atmospheric temperature detection means or/and the temperature of the electric storage means detected by said temperature detection means.
With such a control device for the front and rear wheel drive vehicle, utilizing the atmospheric temperature as the parameter for changing over the control modes with the control mode changeover means makes it possible to estimate the road surface condition at a high accuracy. Further, the control device utilizes the temperature of the electric storage means as the parameter for changing over the control modes with the control mode change over means, enabling the performance of the electric storage means to be accurately estimated. In addi
Nakasako Tooru
Tamenori Kouji
Uchiyama Naoki
Arent Fox Kintner & Plotkin & Kahn, PLLC
Chin Gary
Honda Giken Kogyo Kabushiki Kaisha
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