Hybrid drive system wherein clutch in engaged when engine speed has exceeded motor speed upon switching from motor drive mode to engine drive mode

A method for controlling a hybrid drive system for an automotive vehicle, said hybrid drive system comprising:

• (a) an engine operable by combustion of a fuel to generate a drive force;
• (b) an electric motor;
• (c) an output member operatively connected to a drive wheel of the vehicle for driving the vehicle;
• (d) a planetary gear device having a first rotary element connected to said engine, a second rotary element connected to said electric motor, and a third rotary element;
• (e) a first clutch through which said second rotary element is connected to said output member;
• and (f) a second clutch through which said third rotary element is connected to said output member, said method comprising the steps of:
• engaging said first clutch and releasing said second clutch to thereby establish a forward motor drive mode in which the automotive vehicle is driven in a forward direction by operation of said electric motor while said engine is at rest;
• engaging at least said second clutch to establish a forward engine drive mode in which the automotive vehicle is driven in the forward direction by operation of said engine;
• and
• switching a vehicle drive mode from said forward motor drive mode to said forward engine drive mode, by initiating an engagement of said second clutch only after an operating speed of said engine has exceeded an operating speed of said electric motor.

A hybrid drive system for an automotive vehicle, comprising:

• (a) an engine operable by combustion of a fuel to generate a drive force;
• (b) an electric motor;
• (c) an output member operatively connected to a drive wheel of the vehicle for driving the vehicle;
• (d) a planetary gear device having a first rotary element connected to said engine, a second rotary element connected to said electric motor, and a third rotary element;
• (e) a first clutch through which said second rotary element is connected to said output member;
• (f) a second clutch through which said third rotary element is connected to said output member;
• (g) forward-motor-drive control means for engaging said first clutch and releasing said second clutch to thereby establish a forward motor drive mode in which the automotive vehicle is driven in a forward direction by operation of said electric motor while said engine is at rest;
• (h) forward-engine-drive control means for engaging at least said second clutch to establish a forward engine drive mode in which the automotive vehicle is driven in the forward direction by operation of said engine;
• and
• (i) means operable upon switching of a vehicle drive mode from said forward motor drive mode to said forward engine drive mode,(for initiating an engagement of said second clutch only after an operating speed of said engine has exceeded an operating speed of said electric motor.