Interrelated power delivery controls – including engine control – Transmission control – Engine controlled by transmission
Reexamination Certificate
1999-10-21
2001-11-27
Estremsky, Sherry (Department: 3681)
Interrelated power delivery controls, including engine control
Transmission control
Engine controlled by transmission
C477S110000, C477S037000
Reexamination Certificate
active
06322478
ABSTRACT:
FIELD OF THE INVENTION
This invention relates to transmission control systems for vehicles and in particular to a transmission control system for a continuously variable transmission suitable for use in a vehicle; to a method of controlling such a transmission control system; and to a vehicle having such a transmission control system.
BACKGROUND OF THE INVENTION
It is known to control a continuously variable transmission (CVT) by operating an associated prime mover at its optimum efficiency and by continually varying the output ratio of the transmission to fulfill the demands for torque output placed on the powertrain. It is an object of the control systems for some known CVTs to provide a smooth output from the transmission throughout the operating range of the powertrain.
When such a CVT is fitted to a vehicle, it is usually the aim of the designer to ensure that the CVT has as smooth a torque output as possible. In this way, a user experiences a power delivery which is refined and seamless, i.e. devoid of step changes. One such prior art system is disclosed in U.S. Pat. No. 4,653,005.
For some applications, however, it is desirable to provide noticeable changes in powertrain output, in order to provide powertrain feedback to the user. For example, in a sports car it is often perceived that the driving experience should involve feedback from the powertrain at points in the power delivery which would simulate drops and/or surges in torque around gear shifts and thus be reminiscent of the manual gear shifts beloved of some users of traditional or classic sports cars.
It is an object of this invention to provide: an improved transmission control system for a continuously variable transmission suitable for use in a vehicle; a method of controlling such an improved transmission control system; and to provide a vehicle having such an improved transmission control system.
SUMMARY OF THE INVENTION
According to the invention there is provided a transmission control system for a vehicle comprising a prime mover control means arranged in use to control the torque output from a prime mover and a transmission control means arranged in use to control a continuously variable transmission so as to operate in a plurality of substantially discrete ratios and to control shifts between said ratios, characterised in that the transmission control means is arranged to provide a shift signal to the prime mover control means indicative of a shift between said ratios and the prime mover control means is arranged to temporarily alter said torque output in response to said shift signal, whereby in use a user is provided with feedback which is indicative of said shift and which is in the form of a substantially stepped change in said torque output.
The prime mover control means may be arranged to alter said torque output by reducing it and may be arranged to raise said torque output at the end of a shift between said ratios.
The prime mover control means may be arranged to alter said torque output by increasing it and may be arranged to reduce said torque output at the end of a shift between said ratios.
The prime mover control means may be arranged to alter said torque output substantially for the duration of each shift between said ratios.
The transmission control means may comprise a manual input means for manual selection of shifts between said ratios.
The prime mover may comprise an engine and the prime mover control means may be arranged to alter said torque output by varying the supply of fuel to a cylinder of said engine.
The prime mover may comprise a spark ignition engine and the prime mover control means may be arranged to alter said torque output by varying the ignition timing of said engine.
The prime mover may comprise an engine and the prime mover control means may be arranged to alter said torque output by varying the supply of air to a cylinder of said engine.
The prime mover may comprise an electrical machine and the prime mover control means may be arranged to alter said torque output by varying an electrical supply of said electrical machine.
The invention also provides a vehicle having a transmission control system according to the invention.
The invention also provides a method of controlling a transmission control system for a vehicle comprising a prime mover control means arranged in use to control the torque output from a prime mover and a transmission control means arranged in use to control a continuously variable transmission so as to operate in a plurality of substantially discrete ratios and to control shifts between said ratios, characterized in that the method includes the steps of:
a) providing a shift signal from the transmission control means to the prime mover control means indicative of a shift between said ratios; and
b) altering temporarily said torque output in response to said shift signal;
whereby in use a user is provided with feedback which is indicative of said shift and which is in the form of a substantially stepped change in said torque output.
The method may include altering said torque output by reducing it and may include raising said torque output at the end of a shift between said ratios.
The method may include altering said torque output by increasing it and may include reducing said torque output at the end of a shift between said ratios.
The method may include altering said torque output substantially for the duration of each shift between said ratios.
The method may include manually selecting shifts between said ratios using a manual input means comprising part of the transmission control means.
The prime mover may comprise an engine and the method may include altering said torque output by varying the supply of fuel to a cylinder of said engine.
The prime mover may comprise a spark ignition engine and the method may include altering said torque output by varying the ignition timing of said engine.
The prime mover may comprise an engine and the method may include altering said torque output by varying the supply of air to a cylinder of said engine.
The prime mover may comprise an electrical machine and the method may include altering said torque output by varying an electrical supply of said electrical machine.
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patent: 4653005 (1987-03-01), Osanai et al.
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patent: 5042324 (1991-08-01), Suzuki
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patent: 5517410 (1996-05-01), Nakagawa et al.
patent: 5749804 (1998-05-01), Toukura
patent: 6007452 (1999-12-01), Sawada et al.
patent: 6027425 (2000-02-01), Sakaguchi et al.
patent: 6030313 (2000-02-01), Sawada et al.
patent: 6102831 (2000-08-01), Wakahara et al.
patent: 4120540 (1991-06-01), None
patent: 0530381 (1993-03-01), None
patent: 407223465 (1995-08-01), None
patent: 94/24463 (1994-10-01), None
Davis & Bujold P.L.L.C.
Estremsky Sherry
Lewis Tisha D.
Rover Group Limited
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