Dual strategy control for a toroidal drive type continuously variable transmission
First Claim
1. A continuously variable transmission comprising:
- an input shaft;
an output shaft;
a continuously variable drive section connected between said input shaft and said output shaft, said continuously variable drive section including a roller that is mounted on a trunnion for movement therewith, wherein movement of said roller causes a change in a ratio provided by said continuously variable drive section between said input shaft and said output shaft;
a control system for selectively operating said continuously variable drive section in a torque control strategy under first predetermined operating conditions and in a ratio control strategy under second predetermined operating conditions.
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Abstract
An apparatus and method for operating a continuously variable transmission (CVT), such as a toroidal drive type transmission, is disclosed. The CVT is selectively operated in either a torque control strategy and a ratio control strategy, depending upon the operating conditions of the vehicle. Thus, the CVT is operated in such a manner as to benefit from the advantageous aspects of both the torque and ratio control strategies, while avoiding the disadvantageous aspects of both strategies. The transition from the torque control strategy to the ratio control strategy (and vice versa) can be accomplished by simultaneously calculating the control pressures that would result from operation in both the torque and ratio control strategies, and further assigning a weighted value to each of such calculated control pressures based upon the current operating conditions. The summation of such weighted values provides a composite control signal that facilitates a smooth transition between the two control strategies. The transition from the torque control strategy to the ratio control strategy preferably occurs before a mode shift is effected. Negative feedback is provided in response to ratio changes effected by the control signals to increase stability and to compensate for sensitivity differences at different ratio angles, loading, speeds, and temperatures.
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Citations
17 Claims
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1. A continuously variable transmission comprising:
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an input shaft;
an output shaft;
a continuously variable drive section connected between said input shaft and said output shaft, said continuously variable drive section including a roller that is mounted on a trunnion for movement therewith, wherein movement of said roller causes a change in a ratio provided by said continuously variable drive section between said input shaft and said output shaft;
a control system for selectively operating said continuously variable drive section in a torque control strategy under first predetermined operating conditions and in a ratio control strategy under second predetermined operating conditions. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8)
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9. A continuously variable transmission comprising:
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an input shaft;
an output shaft;
a continuously variable drive section connected between said input shaft and said output shaft, said continuously variable drive section including a roller that is mounted on a trunnion for movement therewith, wherein movement of said roller causes a change in a ratio provided by said continuously variable drive section between said input shaft and said output shaft;
a control system that is responsive to an input signal for effecting movement of said trunnion and said roller; and
a feedback mechanism that is responsive to movement of said trunnion and said roller for causing said control system to alter the movement of said trunnion. - View Dependent Claims (10, 11, 12, 13)
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- 14. The continuously variable transmission defined in claim 14 wherein said feedback mechanism includes a cam that is connected to said trunnion for movement therewith and a link that extends between said cam and said trunnion control valve such that movement of said cam with said trunnion causes movement of said link for varying the operation of said trunnion control valve.
Specification