Dynamic speed governing of a vehicle

Details Dynamic speed governing of a vehicle Dynamic speed governing of a vehicle

1998-05-20

2001-01-02

Johnson, Brian L. (Department: 3618)

Motor vehicles

With means responsive to speed of vehicle for maintaining...

C180S179000, C123S357000, C060S431000

Utility Patent

active

06167979

ABSTRACT:

BACKGROUND OF THE INVENTION
The present invention relates to speed governing techniques for vehicles powered by an internal combustion engine.
In recent years, the implementation of computerized control systems has improved the performance of vehicles powered by an internal combustion engine. Nonetheless, one persistent limitation of these control systems has been the ability to respond smoothly to changes in operating speed under certain conditions. For example, a smooth response for heavy vehicles, such as buses and trucks, is difficult to obtain because this type of vehicle tends to be underpowered and typically lacks the capability to accelerate quickly in response to speed changing conditions as compared to passenger cars. One reason for this difference is because the horsepower/mass ratio for heavy vehicles is generally different than passenger cars; and therefore, heavy vehicle control techniques must compensate for this difference. Additionally, the horsepower/mass ratios for heavy vehicles may vary over a wide range due to wide load variations. Still further, the number of gears in a heavy vehicle varies considerably compared to most passenger vehicles. For these reasons, heavy vehicle control systems are generally more sophisticated than for automobiles.
Also, for heavy vehicles which are equipped with diesel-fueled engines, the heavy vehicle control system typically must cooperate with a fuel control of the particular engine as well as a throttle control, unlike most passenger cars. The fuel control of a diesel engine is typically one or two types of governors: (1) a torque-based governor or (2) an all-speed governor.
A torque governor is configured so that the position of the throttle control generally corresponds to a given level of engine torque. For this type of governor, maintenance of a constant vehicle speed typically requires adjustment of the throttle position in response to variations in the incline and decline of the road. For diesel truck engines, this type of throttle governing configuration is sometimes referred to as a “min-max” governor because it typically limits both the minimum and maximum engine speed but does not directly regulate the engine speed between these limits.
In contrast, an all-speed governor regulates engine speed throughout a continuous engine speed range. This type of governor is commonly used in truck engines, where the throttle position is directly equated to engine speed rather than engine torque. One variety of “all-speed” governor is known as an “isochronous” governor. For the isochronous governor, a constant engine speed is provided for a constant throttle position, regardless of load. A strictly isochronous all-speed governor is not normally used for on-highway applications because small changes in throttle position correspond to large changes in engine torque, making it difficult to operate a vehicle smoothly. As a result, all-speed governors are typically modified to include a “droop” which permits a steady state engine speed to slightly decrease as engine load increases. Nonetheless, if the throttle position is moved too quickly the all-speed governor will constantly counteract the action and hunt to bring the system back into equilibrium. U.S. Pat. No. 5,553,589 to Middleton et al. provides further information concerning these types of governing arrangements.
While the all-speed governor is generally preferred as a more dynamic and responsive regulator, it also tends to have certain drawbacks. For example, it can be difficult to automatically maintain a desired vehicle speed with an all-speed governor. Also, the all-speed governor behaves undesirably when combined with certain types of nonmanual transmissions. These drawbacks are generally due to the fact that the vehicle speed error is a function of the engine speed error, to which the all-speed governor responds, and transmission gear ratio. Smooth vehicle speed is difficult to maintain due to gear shifting because the relationship between vehicle speed and engine speed changes as gears are shifted. Therefore, there is a need for a speed governing technique that better accommodates nonmanual transmissions—especially for heavy vehicles equipped with diesel-fueled engines. The present invention satisfies these needs and provides other important benefits and advantages.
SUMMARY OF THE INVENTION
The invention relates to governing techniques for vehicles powered by an internal combustion engine. Various aspects of the invention are novel, nonobvious, and provide various advantages. While the actual nature of the invention covered herein can only be determined with reference to the claims appended hereto, certain features which are characteristic of the preferred embodiment disclosed herein are described briefly as follows.
One feature of the present invention is a speed control technique which adjusts an engine powering the vehicle in accordance with a difference between an operator-selected vehicle speed and detected vehicle speed. This technique may include determining the operator-selected vehicle speed from a relationship or schedule characterizing a throttle control setting in terms of a range of desired vehicle speeds. This technique is particularly well suited to heavy-duty vehicles equipped with diesel-fueled engines and nonmanual transmissions to maintain a constant vehicle speed for a given throttle position. As used herein, a “nonmanual transmission” includes any type of transmission which does not require an operator to manually shift between each available gear. Examples of nonmanual transmissions include a fully automatic transmission and a semi-automatic transmission, such as shift-by-wire transmission. One type of shift-by-wire transmission is provided by Eaton Corporation under the Trademark AUTOSHIFT. The techniques of the present invention may also be utilized in vehicles having a manual transmission.
Another feature of the present invention includes operating a vehicle having an operator-adjustable control to select vehicle speed. The control is kept in a selected position by maintaining a bearing contact therewith. A desired speed of the vehicle is determined from a predetermined schedule relating a vehicle speed range to a control position range. An observed speed of the vehicle is detected and operation of the vehicle is adjusted to provide the desired vehicle speed in accordance with a difference between the observed speed and the desired speed. This feature may further include repositioning the control to another position while maintaining the bearing contact to provide another vehicle speed.
An additional feature of the present invention includes a drive train configured to propel a vehicle that has an internal combustion engine and a number of ground engaging wheels. A means for governing operation of the engine as a function of vehicle speed is provided which is responsive to a change in setting of an operator-adjustable throttle control to determine a desired vehicle speed from a predetermined schedule relating throttle setting to vehicle speed. This means adjusts the engine to provide the desired vehicle speed in accordance with a difference of the desired vehicle speed from a detected vehicle speed. The means is operable to govern the engine at all operating speeds of the vehicle including when the vehicle is stopped with the engine running.
Still another feature includes operating a vehicle with an internal combustion engine. The vehicle has an operator compartment providing access to an operator-adjustable throttle control for the engine. Position of this control is monitored to provide a corresponding throttle signal. A filter is applied to the throttle signal to reduce vibration-induced variation. The filter includes a predetermined deadband range to provide a filtered signal that remains generally constant until the throttle signal meets a deadband limit. A desired vehicle speed is determined from the filtered signal and an observed vehicle speed is detected. The desired vehicle speed is compared to the observed vehicle speed to provide

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