Data processing: vehicles – navigation – and relative location – Vehicle control – guidance – operation – or indication – With indicator or control of power plant
Reexamination Certificate
1999-04-27
2001-03-06
Yuen, Henry C. (Department: 3747)
Data processing: vehicles, navigation, and relative location
Vehicle control, guidance, operation, or indication
With indicator or control of power plant
C701S115000, C701S110000, C180S179000
Reexamination Certificate
active
06199006
ABSTRACT:
BACKGROUND OF THE INVENTION
The invention relates to a control system for an internal combustion engines of agricultural or commercial vehicles, in particular for engines of agricultural tractors.
Agricultural tractors are designed with respect to desired values of drawbar force and desired gearbox speeds. A standard tractor for plowing at 6 to 7 kilometers per hour (km/h), for example, is designed for a power output of 100 DIN-kW. In order to apply the necessary drawbar force to the ground, the tractor is equipped with heavy weights and large tires. The lower the operating speed is, the greater the torques that can be transmitted at constant engine power output. At low speeds, for example, below 6 km/h, the components of the driveline are protected against overloads by the slip of the wheels. A standard tractor with an output of 100 DIN-kW can pull a trailer of 20 t on a track that rises 1.5 m in a distance of 100 m (upgrade of 1.5%), at a maximum speed of 50 km/h.
Tractors are increasingly driven longer distances on roads, during which higher speeds are desired. For example, it is desirable for a tractor to pull a trailer of 20 t on an upgrade of 1.5% at a speed of 65 km/h. However, this requires an engine power output of approximately 130 kW. For a speed of 80 km/h approximately 168 kW are required. In order to attain these speeds, the engine, the tractor support structure and all other tractor components must be designed for the stated power output values. For operation in the field, however, the drive system of such a tractor would be over-designed and hence uneconomical. As a point of reference, it can be assumed that an overload of the vehicle components by 10% will reduce their service life by approximately 30%.
With an optimum design differing tractors result for operation on the field and the transport over roads, whose internal combustion engines, drivelines, support structures and other tractor components must be designed for differing power output or load capacity. This is in opposition to the desire to offer tractors at favorable cost for a wide range of applications. Since on the one hand, an efficient and hence low cost manufacturing is possible only with the lowest possible number of models and, on the other hand, the use of over-designed drivelines lead to increased costs.
SUMMARY OF THE INVENTION
An object of the invention is to provide an engine control system which enables a more powerful engine to be used in a tractor with less robust components so that higher transport speeds can be obtained without damaging vehicle driveline components.
This and other objects are achieved by the present invention wherein a control system includes a memory unit in which are stored engine performance maps. The control system transmits control signals as a function of target value inputs (such as provided by a gas pedal) to an electronically controlled fuel injection system to control fuel injection quantity as a function of an engine performance map. The control system includes a vehicle speed sensor and limits or throttles the engine output as a function of the sensed vehicle speed. The invention increases the service life of the driveline and other vehicle components, because it protects such vehicle components from overloads when they are not designed for the maximum possible engine output. In order to avoid overloads on vehicle components, the invention reduces or throttles the engine output, in particular for vehicle speed ranges in which high loads and large torques are generated in the driveline.
The invention makes it possible to provide a single vehicle for differing requirements. Such a vehicle may have an engine with a relatively high power output which permits high transport speeds. The gearbox, the chassis and other vehicle components, however, may be designed for a load that is considerably below the rated output of the engine, for example, components which are adequate for normal field operations. This makes it possible to provide a single tractor type that can meet multiple divergent requirements in high production quantities at reasonable manufacturing costs.
Preferably, the rated power output of the engine is designed for a predetermined maximum vehicle speed. When the vehicle is operated at maximum vehicle speed, there is no limitation of engine power output, aside from the usual inherent power reduction when the rated engine rotational speed is reached. At lower vehicle speeds the engine power output is limited to values that are lower than the rated engine power output. Preferably, the power is limited so that the load capacity of the vehicle components corresponds to each vehicle speed or so that the power does not exceed the load capacity or at least does not significantly exceed it.
An upper speed-drawbar force hyperbolic relationship is defined and stored in an engine performance map memory, which corresponds to the rated power output of the engine and is designed for transport operations at high vehicle speeds for a desired maximum vehicle speed and an associated desired drawbar force value. Furthermore, for an operating condition speed-drawbar force hyperbola, such as a plowing, a lower speed-drawbar force hyperbolic relationship is defined through a predetermined lower vehicle operating speed and a limit drawbar force (DPI) with throttled engine power output and, if necessary, stored in the engine performance map memory. The conformation of the engine power output occurs as a function of the vehicle speed along a smooth equalization or transitional relationship which inter-relates the lower and the upper vehicle speed-drawbar force relationships. The transitional relationship can either be derived by the control system from the upper and the lower speed-drawbar force relationships, or it can be pre-determined and stored in the memory unit.
Graphically, these maps and relationships are represented by hyperbolas, and the smooth curve representing the transitional relationship is preferably tangent to the lower velocity region of the lower speed-drawbar force hyperbola (for example, for 100 kW), and is tangent to the upper velocity region of the upper speed-drawbar force hyperbola (for example, for 168 kW), so that a constant smooth transition between the two hyperbolas results.
Preferably, the maximum power output of the engine is continuously lowered starting from the maximum vehicle speed to the operating speed of the vehicle as a proportional function of the measured vehicle speed in the region between the two speed-drawbar force hyperbolas. The lower operating speed is appropriately between 3 and 12 km/h, and is preferably approximately 7 km/h. Furthermore, the engine power output is throttled at the lower operating speed to a power output value that corresponds to the maximum drawbar force that can be transmitted to the ground (of the drawbar output index DPI). The rated engine output corresponds to maximum vehicle speeds between 60 km/h and 90 km/h (preferably approximately 80 km/h) where the reference point is for operation on an upgrade on a slope of 1.5% and with a trailer weighing approximately 20 tons.
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“John Deere Construction Equipment—Motor Graders”.
“Power Tech 10.5/12.5” Diesel Engines, dated Apr. 98.
Burk Ronnie Franklin
Weiss Heinz
Deere & Company
Vo Hieu T.
Yuen Henry C.
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