Clutch control device for four-wheel-drive vehicle

A vehicle clutch control device for a four-wheel drive vehicle having a pair of main drive wheels connected to a driving source and a pair of-auxiliary drive wheels selectively connected to the driving source, the clutch control device comprising:

• a drive mode switching unit configured to perform a switching control of a drive mode of the vehicle based on a vehicle state;
• a dog clutch operatively disposed in a transmission path between the main drive wheels and the auxiliary drive wheels to separate a system for transmitting drive force to the auxiliary drive wheels from a system for transmitting drive force to the main drive wheels by releasing the dog clutch;
• and
• a friction clutch operatively disposed in the transmission path between the main drive wheels and the auxiliary drive wheels to allocate a portion of the drive force from the driving source to the auxiliary drive wheels in accordance with a clutch engagement capacity of the friction clutch, the friction clutch being housed in a clutch case having a clutch chamber and an oil chamber, the clutch chamber containing the friction clutch, the oil chamber being separated from the clutch chamber by a partition wall, the clutch case further including an oil passage through which lubricating oil from the clutch chamber flows into the oil chamber due to a centrifugal force generated in response to rotation of the friction clutch and by operation of an on-off valve disposed in the partition wall,
• the drive mode switching unit being configured to switch the drive mode of the vehicle between a disconnect two-wheel drive mode, a connect four-wheel drive mode and a stand-by two wheel drive mode, the dog clutch and the friction clutch being released in the disconnect two-wheel drive mode, the dog clutch and the friction clutch being engaged in the connect four-wheel drive mode, the dog clutch being engaged and the friction clutch being released in the stand-by two wheel drive mode,
• the drive mode switching unit is configured to bring the friction clutch in a completely released state in the stand-by two-wheel drive mode to enhance fuel efficiency, and
• the drive mode switching unit is further configured to bring the friction clutch in a released state immediately before connection to enhance four-wheel drive performance while in the stand-by two-wheel drive mode,
• the drive mode switching unit being further configured to close the on-off valve so that lubricating oil is stored in the oil chamber to enhance fuel efficiency in the stand-by two-wheel drive mode, and
• the drive mode switching unit being further configured to open the on-off valve so that lubricating oil flows from the oil chamber into the clutch chamber to enhance four-wheel drive performance in the stand-by two-wheel drive mode.

A vehicle clutch control device for a four-wheel drive vehicle having a pair of main drive wheels connected to a driving source and a pair of-auxiliary drive wheels selectively connected to the driving source, the clutch control device comprising:

• a drive mode switching unit configured to perform a switching control of a drive mode of the vehicle based on a vehicle state;
• a dog clutch operatively disposed in a transmission path between the main drive wheels and the auxiliary drive wheels to separate a system for transmitting drive force to the auxiliary drive wheels from a system for transmitting drive force to the main drive wheels by releasing the dog clutch;
• and
• a friction clutch operatively disposed in the transmission path between the main drive wheels and the auxiliary drive wheels to allocate a portion of the drive force from the driving source to the auxiliary drive wheels in accordance with a clutch engagement capacity of the friction clutch,
• the drive mode switching unit being configured to switch the drive mode of the vehicle between a disconnect two-wheel drive mode, a connect four-wheel drive mode and a stand-by two wheel drive mode, the dog clutch and the friction clutch being released in the disconnect two-wheel drive mode, the dog clutch and the friction clutch being engaged in the connect four-wheel drive mode, the dog clutch being engaged and the friction clutch being released in the stand-by two wheel drive mode,
• the drive mode switching unit being further configured to switch the drive mode of the vehicle to the disconnect two-wheel drive mode in a condition during which a vehicle speed is higher than a predetermined threshold vehicle speed that is greater than zero and a required driving force is lower than a predetermined threshold driving force,
• the drive mode switching unit is further configured to switch the drive mode of the vehicle to the stand-by two-wheel drive mode in a condition during which the vehicle speed is higher than the predetermined threshold vehicle speed and the required driving force is higher than the predetermined threshold driving force, and
• the drive mode switching unit is further configured to switch the drive mode of the vehicle to the connect four-wheel drive mode in a condition in which the vehicle speed is lower than the predetermined threshold vehicle speed.