Hybrid drive apparatus for vehicle

DETAILED DESCRIPTION Accordingly, a first object of the invention is to provide a hybrid drive apparatus for a vehicle which is capable of making a cranking characteristic at the restart of the engine constant so that the engine is restarted with a good response under a simple control in a state where the vehicle is driven by the motor generator.
A second object of the invention is to realize a standby state by hydraulic control for making the cranking characteristic constant.
A third object of the invention is to enable the standby state for making the cranking characteristic constant and to realize the subsequent starting in a limited range of output from the motor generator.
In order to prevent a shock owing to the decrease in the driving force at the restart of the engine, a motor generator having a large capacity for outputting a sufficiently great torque must be employed.
Moreover, control for increasing the output torque in accordance with the cranking load must be performed.
If the motor generator having the large capacity is mounted only to start the engine, the size of the motor generator becomes unnecessarily enlarged.
The capacity of an inverter for controlling the motor generator is accordingly increased, leading to the increased capacity of the battery.
Thus, the above-mentioned method cannot effectively solve the problems.
Accordingly, a fourth object of the invention is to provide a hybrid drive apparatus for a vehicle which employs a starter motor provided for an engine so as to supplementarily be operated to crank the engine at a satisfactory response without enlarging the motor generator for performing cranking under simple control of the engagement pressure of the clutch.
A fifth object of the invention is to provide a hybrid drive apparatus for a vehicle which is capable of realizing a standby state for making the cranking characteristic constant and subsequent start by a motor generator without using a special auxiliary drive means.
A general method is known, which starts an engine by a starter motor