1. Field of the Invention
The present invention relates to a control system for hybrid vehicles which are driven by engines as well as motors, and in particular relates to a hybrid vehicle control system which conducts the control of the heating of a battery during cruise operation.
This application is based on Japanese Patent Application No. Hei 11-230914, the contents of which are incorporated herein by reference.
2. Description of the Related Art
Conventionally, hybrid vehicles which are provided with motors in addition to engines as power sources for operating the vehicles are known.
One type of these hybrid vehicles are parallel hybrid vehicles, in which a motor is employed as an auxiliary power source for assisting the output of the engine. In these parallel hybrid vehicles, various types of control are conducted, such as the assistance of the output of the engine by the motor during acceleration, and the charging of the battery by deceleration regeneration during deceleration, and such vehicles are capable of satisfying the requirements of the driver while maintaining the remaining capacity (electrical energy) of the battery (such a vehicle is disclosed, for example, in Japanese Unexamined Patent Application, First Publication No. Hei. 7-123509).
However, in the conventional hybrid vehicle control system described above, from the point of view of an increase in the charge/discharge efficiency of the battery, and the protection of the battery, as shown in FIG. 15, prespecified upper limits (assist power save line ASSIST and regeneration power save line REGEN) are provided in the amount of assistance and the amount of regenerated power generation produced by the motor in accordance with the temperature of the battery, and these are set so that the acceptance width W of the assistance amount and the regenerated power generation amount decreases as the battery temperature TBAT is lowered. For this reason, when the battery temperature decreases, as after a long period of parking in a cold area, the assistance amount and the regenerated power generation amount are limited to low values.
Here, when acceleration and deceleration operation is conducted in which acceleration and deceleration are repeated, then assistance and the regeneration of power generation are repeatedly conducted by the motor within the range of acceptance width W of the assistance amount and the regenerated power generation amount in accordance with the temperature of the battery, and thereby, the flow of charge current and discharge current into and out of the battery is frequently conducted, Joule heat is generated as a result of the internal resistance of the battery, and the temperature of the battery rises at an early stage. However, when cruise operation is conducted, in which there is little charging or discharging of the battery, the battery is merely heated by the internal heater of the vehicle via a fan or the like, and the heating of the battery is delayed, and thereby, a problem is caused in that the assistance amount and the regenerated power generation amount of the motor are limited to low values.
The present invention was created in light of the above circumstances; it has as an object thereof to provide a hybrid vehicle control system which is capable, during vehicle operation in the cruise mode, of raising the temperature of a battery which is at a low temperature in a short period of time, and increasing the assistance amount and the regenerated power generation amount of the motor.
In order to attain the object of solving the problems described above, in a first aspect of the present invention, a hybrid vehicle control system which is provided with: an engine which outputs the propulsion force of the vehicle; a motor which assists the output of the engine in accordance with the operational state of the vehicle; and an electricity storage device, which stores generated energy, when the motor is employed as a generator by the output of the engine, and regenerated energy, which is produced by the regenerative state of the motor when the vehicle decelerates, comprising: an electricity storage device temperature detector (in the embodiment described hereinbelow, step S102 and step S107) for detecting the temperature of the electricity storage device; an engine water temperature detector (in the embodiment described hereinbelow, step S105) for detecting the engine water temperature which is related to the temperature of the engine; and a power generation increasing device (in the embodiment described hereinbelow, step S103 or step S106) for increasing the amount of generated energy when the motor is used as a generator during vehicle operation by the drive force of the engine, without the output assistance of the engine by the motor in accordance with the operational state of the vehicle, either in the case in which the electricity storage device temperature is detected at or below a predetermined electricity storage device temperature by the electricity storage device temperature detector, or in the case in which the engine water temperature is detected at or below a predetermined temperature by the engine water temperature, detector.
In accordance with the hybrid vehicle control system having the composition described above, during operation of the vehicle in cruise mode, the amount of energy generated by the motor is increased, and thereby, a charging current is supplied to the electricity storage device, and the electricity storage device heats itself by means of the Joule heat generated as a result of the internal resistance of the electricity storage device. By means of this, it is possible to raise the temperature of an electricity storage device which is at a low temperature at an early stage, and by raising the temperature of the electricity storage device, it is possible to increase, at an early stage, the amount of assistance and the amount of regenerated power generation of the motor.
Furthermore, in a second aspect of the present invention, the hybrid vehicle control system further comprising: a remaining capacity detector (in the embodiment described hereinbelow, battery ECU 13) for detecting remaining capacity of the electricity storage device, and an overcharge correcting device (in the embodiment described hereinbelow, step S201) for raising a power generation suppression threshold which serves to suppress generation of electricity by the motor in the case in which the remaining capacity is detected to be in an overcharged state by the remaining capacity detector when in the amount of energy generated by the motor is increased by the power generation increasing device, are provided.
In accordance with the hybrid vehicle control system having the composition described above, during normal control in which the temperature of the electricity storage device is sufficiently high, when a determination is made that the remaining capacity of the electricity storage device is in an overcharged state, then further power generation by the motor is suppressed and further charging of the electricity storage device is not conducted; however, when the electricity storage device is at a low temperature, the power generation suppression threshold which serves to suppress power generation by the motor is raised, and by continuously conducting charging of the electricity storage device, it is possible to increase the internal resistance of the electricity storage device and to generate a large amount of Joule heat, and it is possible to promote the self-heating of the electricity storage device. When the temperature of the electricity storage device is low, even if charging of the overcharged state electricity storage device is continued, it is possible to ignore the possibility of damage to the electricity storage device.
Furthermore, in a third aspect of the invention, the hybrid vehicle control system further comprising: a vibration suppressing controller (in the embodiment described hereinbelow, steps S501-S507) is provided for suppressing vibration of the engine resulting from fluctuations in the drive force of the engine by conducting power generation by the motor when the drive force is increasing and conducting output assistance of the engine by the motor when the drive force is decreasing so as to cancel periodic amounts of fluctuation in the drive force of the engine, in the case in which the remaining capacity is detected by the remaining capacity detector to be in excess of a predetermined remaining capacity threshold value, and a fully charged state is thus detected.
In accordance with the hybrid vehicle control system having the composition described above, when a determination is made that the remaining capacity of the electricity storage device is in a fully charged state, that is to say, that the state is such that further charging can not be accepted, by conducting vibration control which controls the motor so as to cancel the amount of fluctuation in the drive force of the engine, it is possible to leave the load on the engine, and it is possible to increase the engine water temperature. As a result of this, the temperature of the heater within the vehicle rises, and it is possible to increase the temperature of the electricity storage device via a fan or the like. There is no decrease in the load on the engine, so that the fuel consumption temporarily worsen, however, by promoting an increase in the temperature of the electricity storage device, the assistance amount and the regenerated power generation amount of the motor are increased at an early stage, so that it is possible to improve the fuel consumption in terms of the overall operation of the vehicle.