Four-wheel drive vehicle and control apparatus for four-wheel drive vehicle

A four-wheel drive vehicle, comprising:

• main driving wheels to which a driving force of a drive source is constantly transmitted;
• a driving shaft configured to transmit the driving force in a fore-and-aft direction of the vehicle;
• auxiliary driving wheels to which the driving force of the drive source is transmitted via the driving shaft;
• a first driving force transmission apparatus and a second driving force transmission apparatus arranged such that the driving shaft is interposed between the first driving force transmission apparatus and the second driving force transmission apparatus in a driving force transmission path to the auxiliary driving wheels;
• and
• a control apparatus configured to control the first driving force transmission apparatus and the second driving force transmission apparatus, wherein
• the first driving force transmission apparatus includes a dog clutch configured to transmit the driving force through engagement between projections and recesses,
• the second driving force transmission apparatus includes:
• an outer rotational member and an inner rotational member that are supported so as to be coaxially rotatable relative to each other;
• an outer clutch plate configured to rotate together with the outer rotational member;
• an inner clutch plate configured to rotate together with the inner rotational member;
• and
• a pressing mechanism configured to press the outer clutch plate and the inner clutch plate in an axial direction by a pressing force in accordance with a control current supplied from the control apparatus,
• the control apparatus includes:
• a current output circuit configured to output the control current to the pressing mechanism;
• a current detector configured to output a detection signal in accordance with a magnitude of the control current that is actually output from the current output circuit;
• a target current value calculator configured to calculate a target current value that is a target value of the control current to be supplied to the pressing mechanism;
• and
• a current controller configured to control the current output circuit so that the control current having the current value calculated by the target current value calculator based on a result of detection performed by the current detector is output to the pressing mechanism, and
• when the four-wheel drive vehicle is in a two-wheel drive mode in which transmission of the driving force that is performed by both of the first driving force transmission apparatus and the second driving force transmission apparatus is interrupted, the current controller is configured to perform zero-point adjustment for storing information that the detection signal output from the current detector indicates a zero point of the control current to be output from the current output circuit.