Power transmission system

A power transmission system comprising:

• a first speed changer connected to an output shaft of a first power source;
• and
• a second speed changer connected to an output shaft of a second power source, wherein:
• each of the first speed changer and the second speed changer includes plural rotational elements;
• a first rotational element of the first speed changer and a first rotational element of the second speed changer are coupled to each other in a manner permitting integrated rotation and have a same rotational axis;
• the first speed changer includes a second rotational element engaging with the first rotational element;
• an engagement portion between the first rotational element and the second rotational element of the first speed changer is formed such that, when the first power source generates a rotational torque in one direction, a force acts on the first rotational element of the first speed changer in a direction of approaching the second speed changer along the rotational axis direction;
• the second speed changer includes a second rotational element engaging with the first rotational element;
• and
• an engagement portion between the first rotational element and the second rotational element of the second speed changer is formed such that, when the second power source generates a rotational torque in one direction, a force acts on the first rotational element of the second speed changer in a direction of approaching the first speed changer along the rotational axis direction.