Traction pressure control system

For a variable speed transmission having traction engaging drive elements, a drive ratio change mechanism for effecting relative displacement of said drive elements, and a traction pressure regulating device for controlling traction pressure between said drive elements, a system for varying the traction pressure to maintain optimum slip between said drive elements, comprising a plurality of sensing means operatively connected to said drive elements, the traction pressure regulating device and the drive ratio change mechanism for respectively sensing the speed of the drive elements, the traction pressure and the drive ratio position of the mechanism, means connected to the traction pressure sensing means for electronically generating a rate signal corresponding to the ratio of change in slip derived from the sensed speed and the drive ratio position to the traction pressure sensed, means connected to said electronic generating means for selecting a signal band embracing a peak value of the rate signal, and means connected to the traction pressure regulating device and responsive to deviation of the rate signal from said signal band for correctively varying the traction pressure.

For a transmission having input and output members, traction drive elements in engagement with each other under a surface contact pressure to establish a power transmitting path between said input and output members and drive ratio control means operative through said traction drive elements to change the drive ratio of the transmission, a method of varying the surface contact pressure to obtain optimum slip, including the steps of:

• sensing the setting of the drive ratio control means and measuring speed of said input and output members, calculating the actual slippage between said traction drive elements of the transmission from the sensed drive ratio setting and measured speed, comparing empirical data representing optimum slippage for each of the drive ratios with said calculated slippage to determine a slippage error;
• and adjusting the contact pressure to correct said determined slippage error.

In combination with a transmission having input and output members, traction drive elements in engagement with each other under a surface contact pressure to establish a power transmitting path between said input and output members and drive ratio control means operative through said traction drive elements to change the drive ratio of the transmission, the improvement residing in control means for varying the surface contact pressure, including means for sensing the drive ratios established by the drive ratio control means and the actual speed ratios between said input and output members, data processing means connected to said sensing means for calculating the slippage between said traction drive elements for each of the drive ratios of the transmission, means for generating empirical data representing optimum slippage for each of the drive ratios, comparator means connected to said generating means and the data processing means for producing a corrective output signal, and servo means connected to said comparator means for adjusting the contact pressure in response to said corrective output signal.

In a transmission having input and output members, traction drive elements in engagement with each other under a surface contact pressure to establish a power transmitting path between said input and output members and drive ratio control means operative through said traction drive elements to change the drive ratio of the transmission, means for sensing the drive ratios established by the drive ratio control means and the actual speed of said input and output members, servo means for varying the surface contact pressure, and data processing means connected to said sensing means and the servo means for continuously adjusting the contact pressure to establish an optimum amount of slippage between said traction drive elements at all of the drive ratios of the transmission.