1. Field of Invention
The invention relates to a driving control device of a vehicle, for example, a hybrid vehicle, performing an idling stop and the like.
2. Description of Related Art
In recent years, in order to reduce an exhaust gas, improve a fuel economy and the like, there has been developed various kinds of vehicles, such as a hybrid vehicle, in which an engine automatic stopping control (hereinafter, an engine stopping control) for automatically stopping a driving of an engine is executed at a time when a vehicle stops, for example, while waiting at stoplights or the like during a movement of the vehicle or a predetermined stop condition is established, a vehicle performing an idling stop, and the like. Further, these vehicles are structured such as to restart after the driving of the engine in the vehicle is automatically stopped.
Meanwhile, the vehicle mentioned above is provided with an automatic transmission performing an automatic speed change in accordance with a hydraulic control. In the automatic transmission, a hydraulic pressure generated by a mechanical oil pump driven by an engine or a motor is controlled by a hydraulic control device. Then, engagement and disengagement of a predetermined number of frictional engagement elements are controlled in accordance with a predetermined speed change control on the basis of a vehicle traveling condition or the like by the controlled hydraulic pressure, whereby the automatic speed change control is performed.
However, in the vehicle mentioned above, the mechanical oil pump stops together with the driving source at a time when the engine driving is automatically stopped. Accordingly, when the engine driving is automatically stopped, the hydraulic pressure supplied from the mechanical oil pump is reduced, and it is impossible to maintain a predetermined hydraulic pressure necessary for engaging the frictional engagement element. When the engine is restarted under a state in which the hydraulic pressure of the hydraulic control device can not be maintained in the predetermined hydraulic pressure, a lot of time is required until the hydraulic pressure is increased, so that a lot of time is required until the frictional engagement element is engaged, and a response is deteriorated.
Further, since the mechanical oil pump is also restarted, the hydraulic pressure supplied from the mechanical oil pump to the hydraulic control device is increased. Further, when the hydraulic pressure supplied to the hydraulic control device is increased to the predetermined hydraulic pressure, the frictional engagement element mentioned above is again engaged. Accordingly, a shock is generated.
Accordingly, there is proposed, for example, in Japanese Patent Publication No. 8-14076, an automatic transmission structured such that an electric oil pump provided with a motor independent from the driving source of the vehicle is provided separately from the mechanical oil pump mentioned above, and a predetermined hydraulic pressure necessary for engaging the frictional engagement element is maintained in the hydraulic control device by driving the electric oil pump so as to supply the hydraulic pressure to the hydraulic control device at a time when the mechanical oil pump is stopped.
In accordance with the automatic transmission disclosed in this Publication, since it is possible to maintain the hydraulic pressure of the hydraulic control device in the predetermined hydraulic pressure necessary for engaging the frictional engagement element by the electric oil pump, even at a time of the automatic stop of the mechanical oil pump, the frictional engagement element engaged at the starting time can be securely set in the engagement state, and it is possible to prevent the shock at a time of engaging the frictional engagement element.
However, in the automatic transmission in the Publication mentioned above, in order to operate the electric oil pump so as to secure the clutch hydraulic pressure in order to have no engagement shock at a time of restarting the engine as mentioned above during the automatic stop of the driving of the vehicle engine, a high torque motor is required. A high motor torque is required because a viscosity of an automatic transmission oil (hereinafter, refer also to ATF) is increased and a drive load (torque) of the electric oil pump is increased at a low oil temperature (a low oil temperature in comparison with an oil temperature in a normal use) of the ATF. Further, since the viscosity of the ATF is reduced and a consumption flow rate of the ATF in the automatic transmission (A/T) is increased reversely at a high oil temperature (a high oil temperature in comparison with the oil temperature in the normal use) of the ATF, a high rotation motor is required. Accordingly, in order to operate the electric oil pump in such a manner as to prevent the engagement shock from being generated at a time of restarting the engine in all of the oil temperature ranges, an increase in size of the electric oil pump is caused.
Further, when operating the electric oil pump under a severe condition of the low oil temperature or the high oil temperature, there can also be considered that problems may generate such that the operation time of the electric oil pump is reduced, a durability of the electric oil pump is reduced, and the like.
Further, when the electric oil pump fails and can not be used, it is impossible to supply the hydraulic pressure by the electric oil pump, and it is impossible to supply the hydraulic pressure for engaging the frictional engagement element at the engine stop time. Therefore, there is similarly generated a problem that the shock is generated at a time of reengaging the frictional engagement element.
The invention is thus made by taking the foregoing situation into consideration, and the invention thus provides a driving control device of a vehicle which can reduce a shock generated by an engagement of a frictional engagement element without requiring an increase in the size of an electric oil pump, even at a time when the electric oil pump can not be driven. For example, at a time of the low oil temperature or the high oil temperature as mentioned above during an automatic stop of the engine driving in the vehicle, or at a time when the electric oil pump can not be used.
In order to solve the foregoing, a driving control device of a vehicle according to an exemplary aspect of the invention includes an automatic transmission that transmits a driving force of an engine to a wheel by engaging a frictional engagement element, the automatic transmission including a hydraulic control device which hydraulically controls an engagement of the frictional engagement element, a mechanical oil pump which is driven by the engine and supplies hydraulic pressure to the hydraulic control device and an electric oil pump which supplies hydraulic pressure to the hydraulic control device and a motor connected to the mechanical oil pump and transmitting the driving force to the automatic transmission, wherein the electric oil pump supplies oil to the hydraulic control device at an engine automatic stopping control time at which the driving of the engine is automatically stopped after the vehicle stops and a predetermined condition is established and the motor is driven so that said mechanical oil pump supplies the oil to the hydraulic control device during the engine automatic stopping control at a time when the electric oil pump can not be driven.