Interrelated power delivery controls – including engine control – Transmission control – Continuously variable friction transmission
Patent
1996-03-29
1998-10-13
Ta, Khoi Q.
Interrelated power delivery controls, including engine control
Transmission control
Continuously variable friction transmission
477 46, F16H 6138
Patent
active
058205136
DESCRIPTION:
BRIEF SUMMARY
FIELD OF THE INVENTION
This invention relates to vehicular drivelines including a continuously-variable-ratio transmission, or CVT, the input of which is connected to an engine or other prime mover, and the rotary output of which will be referred to as the final drive.
While the invention is applicable to boats, aircraft, railed and other vehicles in general, it applies particularly to drivelines for automobile vehicles, in which the final drive is connected to the driven wheel or wheels. And while the invention is also applicable to vehicular drivelines including other types of CVT, for instance those of belt-driven, Kopp, or Beier type, and in which the ratio-varying element may be directly and mechanically controlled to determine the instantaneous ratio.
The invention applies particularly to CVTs of the toroidal-race rolling-traction type in which there is no such direct mechanical control upon the rollers. Instead the angular setting to which they settle, and thus the ratio that they transmit, is determined by a balance between the resultant torque to which they are subjected, and the operating force applied to the carriages in which they are mounted. Such toroidal-race CVTs are now known in the art as being of "torque-controlled" type, and recent examples are described for instance in Patents GB-B-2227287 and GB-B-0356102.
It is also now well understood in the art to control such drivelines so that the engine performs at all times in conformity with an electronic "map" constructed to optimise efficiency in some form. FIG. 1 of the accompanying drawings is a typical graph in which the y-axis represents engine torque T and the x-axis engine speed N, with the hyperbolae 1 indicating lines of constant power. Ordinates 2 and 3 indicate idling and maximum engine speeds respectively. Function 4 represents the maximum torque of which the engine is capable over its full range of working speeds. Function 5 represents the preferred and predetermined "control line", to which the engine is programmed to work when under power demand, to achieve optimum performance according to a chosen criterion. That criterion may for instance be optimum emission characteristics, or least knock. With sophisticated control systems, an engine can be programmed to work to alternative control lines from which the driver can select. Typically, and as shown in FIG. 1, function 5 is chosen to achieve maximum power per unit of fuel consumed. Function 8 indicates the typical correlation of T and N when demand is withdrawn and the engine is over-running.
BRIEF DESCRIPTION OF THE DRAWING(S)
The invention will now be described, by way of example, with reference to the accompanying drawings, in which:
FIG. 1 is a graph of engine torque versus engine speed and indicates a desired performance map function;
FIG. 2 is a graph of engine speed, N, verses vehicle speed, V, and indicates an effective conventional range within which a vehicle is capable of working;
FIG. 3 is also a graph of engine speed, N, verses vehicle speed, V, but illustrates two modes of operation according to the invention;
FIG. 4 is a graph correlating engine speed, N, with accelerator position, P; and
FIG. 5 is a block diagram of the driveline which includes a prime mover, a CVT and a final drive.
DESCRIPTION OF THE PREFERRED EMBODIMENT(S)
The graph of FIG. 2 illustrates the typical correlation of engine speed N (y-axis) and vehicle speed V (x-axis) in an automotive vehicle driveline where the engine is controlled as indicated in FIG. 1, and where the driven wheels of the vehicle are the final drive. Lines 9 and 10 correspond to ordinates 2 and 3 of FIG. 1, and the sloping linear function 11 (which passes through the origin 0) corresponds with first gear ratio in a typical fixed-ratio transmission and thus defines the effective minimum values of N and V at which it is judged desirable for the driveline to work in practice. Ordinate 12 marks the maximum safe value of V. The effective "area" within which the driveline is capable of working is therefore bounded by lines 9,
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Ta Khoi Q.
Torotrak (Development) Limited
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