FOUR-WHEEL DRIVE VEHICLE CLUTCH CONTROL METHOD AND CLUTCH CONTROL DEVICE
FIG3 is a perspective view and an action schematic view showing a cam mechanism in the electronically controlled ball-cam-type coupling
An action for engaging the electronically controlled ball-cam-type coupling 10 is described below on the basis of FIG3. First, when a coil current is made to flow to the 4WD solenoid 24 by the solenoid command current from the 4WD controller 16, a magnetic field is generated around the 4WD solenoid 24 and an armature 30 is caused to be drawn toward the control clutch 31. Friction torque is generated by the control clutch 31 upon being pressed by the armature 30 drawn thereto, and the friction torque generated by the control clutch 31 is transmitted to the control cam 32 of the cam mechanism to become a circumferential-direction binding force F1. The circumferential-direction binding force F1 applied to the control cam 32 is amplified and converted to an axial-direction clutch pressing force F2 via the cam grooves 36, 36 and the balls 34, and the main cam 33 is pressed frontward. Thus, due to the clutch pressing force F2 from the main cam 33 pressing and engaging the main clutch 35, clutch engagement torque that is proportional to the solenoid command current is generated in the main clutch 35. The clutch engagement torque generated in the main clutch 35 is transmitted to the rear differential 11 through the coupling output shaft 28.
perspective view
28
coupling output shaft
17
mode-switching switch
35
main clutch
30
armature
34
balls
33
main cam
10
coupling
29
coupling housing
36
cam grooves
31
control clutch
32
control cam
['3. The four-wheel-drive vehicle clutch control method as claimed in claim 1 or 2,  characterized in that the friction clutch is an electronically controlled ball-cam-type coupling; and when a shift-position-switching operation is performed between an advancing travel shift position and a reversing travel shift position while the vehicle  is stopped, reducing the initial torque that had been applied before the shift-position-switching operation to or below a prescribed value.']