Driving force distribution device

A driving force distribution device for a four-wheel drive vehicle, the driving force distribution device variably distributing driving force between front and rear wheels, the driving force distribution device being capable of distributing the driving force between right and left wheels of one of the front and rear wheels to independently control an engagement force of each of right and left clutches corresponding to the right and left wheels, the driving force distribution device comprising:

• wheel speed sensors each detecting rotational speed of each of the right and left wheels to which the driving force can be distributed;
• a front and rear wheel power control section that sets up a limit value for limiting driving force transmitted from a driving source to the one of the front and rear wheels in the case where a difference between the rotational speeds of the right and left wheels detected by the wheel speed sensors is less than a predetermined value;
• and
• a right and left wheel power transmission control section for distributing the transmitted driving force between the right and left wheels of the one of the front and rear wheels,
• wherein, in the case where the difference between the rotational speeds of the right and left wheels detected by the wheel speed sensors is less than the predetermined value, the right and left wheel power transmission control section distributes the transmitted driving force between the right and left wheels so that a total value of the driving forces of the right and left wheels does not exceed the limit value set up by the front and rear wheels power transmission control section, and the right and left wheel power transmission control section controls the engagement force of each of the right and left clutches corresponding to the right and left wheels in accordance with the transmitted driving force distributed for each of the right and left clutches, and
• wherein, in the case where the difference between the rotational speeds of the right and left wheels detected by the wheel speed sensors is the predetermined value or more, the right and left wheel power transmission control section distributes the transmitted driving force between the right and left wheels so that the driving force up to a driving force upper limit, which is set up in advance, is transmitted for each wheel to the respective right and left rear wheels regardless of the total value of the driving forces of the right and left rear wheels, and the right and left wheel power transmission control section controls the engagement force of each of the right and left clutches corresponding to the right and left wheels in accordance with the transmitted driving force distributed for each of the right and left clutches,
• wherein the limit value is less than a sum of the driving force upper limits of the right and left rear wheels.