Interrelated power delivery controls – including engine control – Transmission control – With brake control
Reexamination Certificate
2000-04-07
2001-09-04
Wright, Dirk (Department: 3681)
Interrelated power delivery controls, including engine control
Transmission control
With brake control
Reexamination Certificate
active
06283891
ABSTRACT:
TECHNICAL FIELD
The invention relates to the control of ratio changes in a multiple-ratio automatic transmission for an automotive vehicle driveline.
BACKGROUND ART
It is known design practice to modify an automotive vehicle driveline to adapt it for drag-race applications. This typically would require incorporating a transmission brake function within the transmission housing to lock the transmission in a static condition when the vehicle brakes are applied and the engine throttle is advanced at the initiation of a launch of the vehicle. The internal transmission lock permits the operator to hold the vehicle at the starting line while applying full engine torque. The wheel brakes normally would lack sufficient braking capacity for such conditions.
Such modifications to the transmission for drag-race applications involve extensive redesign of the transmission to accommodate an internal transmission lock. At the instant of the launch, the internal transmission lock is released. This allows maximum launch acceleration to be achieved since the engine is held at its optimum stall speed prior to the launch.
The stall speed of the engine is determined by the torque converter size factor and by the engine torque available. The torque converter size factor, a well known design characteristic, is equal to the engine speed divided by the square root of the turbine torque.
The vehicle brakes and the internal transmission lock are applied as the throttle is advanced to a position at or near the wide-open throttle position. Takeoff or launch occurs as the vehicle brakes and the internal transmission lock are released.
In a typical driveline that has been modified for drag-race applications, the vehicle can be maintained in the stalled state at launch with the engine operating at a higher power level only if additional braking is provided to complement the wheel braking.
DISCLOSURE OF INVENTION
The invention is adapted particularly to be used with multiple-ratio automatic transmissions for automotive vehicles in which ratio changes are under the control of a driveline electronic controller. The controller responds to changes in driveline variables, including throttle position, engine speed, vehicle speed and turbine speed. The control system of the invention has at least two operating modes: (1) a normal automatic ratio-changing mode; and (2) a launch-assist mode wherein the automatic ratio-changing mode is overruled and replaced by a mode in which the transmission is maintained, in a high gear ratio (usually the highest gear ratio), until the launch is initiated.
At the start of the launch, the transmission automatically converts to an automatic upshift mode wherein the lowest gear ratio is activated for maximum acceleration and wherein ratio changes in response to changing operating variables in the driveline take place through the available range of speed ratios. The effective torque at the output shaft of the transmission is reduced at stall because the transmission is held in its optimum speed ratio gear, usually the highest gear ratio. This allows the vehicle brakes to hold the vehicle powertrain in the stall state without the additional braking capacity of an internal transmission brake or lock. When stall state is terminated, the automatic ratio-changing state is initiated in response to the release of vehicle wheel brakes.
After the vehicle stops, the launch-assist mode is terminated and the normal automatic ratio-changing mode is effected. No re-enabling step is needed.
The input signals to the microprocessor driveline controller would include a wheel brake switch activated upon application of the wheel brakes, a vehicle speed sensor, a transmission range sensor, and a driver-activated launch-assist switch. Although the launch-assist switch could be mounted in a driver control module independently of other driveline controls, it could be incorporated into an existing vehicle switch assembly. Other transmission input signals may be a transmission temperature sensor signal, a throttle position sensor signal, an engine speed sensor signal and a torque sensor signal.
Another feature of the invention is a manual upshift sequence capability that is provided by a driver-operated mode selector switch and an enable switch, whereby manually selected upshifts for the vehicle replace the normal automatic shift sequence during a specific run; that is, during an upshift sequence beginning with the lowest speed ratio to the highest speed ratio. This achieves a limited shift point control for drag-race applications without requiring additional transmission control hardware.
Unlike typical drag-racing transmission modifications, a manual upshift sequence can be used to override the normal upshift sequence. This can be done without the use of special shift valve springs, pressure booster valve changes, and line pressure control springs. The necessary modifications to a typical transmission control system involve only software changes in the transmission electronic controller.
When the operator enters the manual upshift mode, manually selected upshifts are substituted for normal scheduled automatic upshifts. The transmission then will upshift only on the driver's command, which may involve activating an upshift enabling switch. When the highest gear ratio is reached, or when the wheel brakes are applied, the manual upshift sequence mode will be discontinued.
A launch-assist and manual upshift mode is available and can be enabled by the driver as the wheel brakes are applied. The method of the invention includes the step of selecting in sequence the speed ratios from the lowest to the highest ratio as the wheel brakes are released and the vehicle accelerates from a standing start. The manual upshift routine is disabled when the highest speed ratio is achieved.
The launch-assist and automatic ratio upshifting mode can be enabled as the brakes are applied. As previously indicated, high speed ratio in the gearing is established at the beginning of the launch-assist before the brakes are released, whereby the torque delivered to the wheels is reduced.
Application of the brakes results in distribution of a brake signal to the controller to terminate the manual upshift sequence and to substitute the normal automatic upshift sequence for which the driveline is calibrated. The enabling switch, which serves as an upshift switch during operation in the manual upshift sequence mode, can be incorporated into an existing vehicle switch, or it may be an independent add-on switch.
A brake signal from a brake sensor, when the wheel brakes are applied, will interrupt the manual upshift sequence mode. The manual upshift sequence mode is interrupted also when the transmission reaches its highest speed ratio.
REFERENCES:
patent: 4645051 (1987-02-01), Maezono et al.
patent: 4665777 (1987-05-01), Kikuchi et al.
patent: 4694709 (1987-09-01), Kikuchi et al.
patent: 5272630 (1993-12-01), Brown et al.
patent: 5642283 (1997-06-01), Schulz et al.
patent: 5646842 (1997-07-01), Schulz et al.
patent: 6007445 (1999-12-01), Kirchhoffer et al.
Lavigne Richard Leon
Wozniak Kenneth Paul
Ford Global Technologies Inc.
McKenzie Frank G.
Wright Dirk
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