| 摘要 |
The invention concerns a traction control arrangement for a variator (10). The variator has a pair of races (12, 14, 26) and at least one roller (28) which is arranged to engage both races and to transfer drive from one to the other. The roller is movabiy mounted and its motion enables the speed of one race to be varied relative to the speed of the other race. The variator has a hydraulic traction load actuator (117) which receives a hydraulic traction load pressure and in response urges the races and the rollers into engagement in order to provide traction between them. At least one hydraulic roller control actuator (32) is arranged to receive opposed first and second reaction pressures and in response to apply a reaction force to the roller. The traction control arrangement has a traction control valve (119, 119a) which controls the traction load pressure and which is operable in at least two modes:- i. in a first mode, it receives (a) a first pilot pressure signal corresponding to the traction load pressure and (b) a second pilot pressure signal corresponding to the higher of the first and second reaction pressures, and controls the traction load pressure in response to the difference between the first and second pilot pressure signals; ii. in a second mode, it receives (a) a first pilot pressure signal corresponding to the traction load pressure, (b) a second pilot pressure signal corresponding to the higher of the first and second reaction pressures, and (c) a third pilot pressure signal corresponding to the lower of the first and second reaction pressures, and controls the traction load pressure as a function of the first, second and third pilot pressure signals. The relationship between traction load pressure and reaction force is different in the two modes and in this way provision is made to selectively alter the traction coefficient in the variator. |
