Patent Application
20050015196
1. Field of the Invention
The present invention relates to control of compression ignition engines with electronic control modules programmable to detect engine overspeed operation, and inhibiting throttle response to throttle activation after detecting overspeed engine operation.
2. Background Art
A vehicle engine may be severely damaged when the engine is driven to an overspeed condition. Of course, the upper limit of the damaging overspeed condition may be different for a variety of engines, and often depends on the number of cylinders, or/and stroke of the cylinders, and other structural parameters of the vehicle engine. Typically engine brakes can be enabled to prevent an engine overspeed condition. Engine compression brake logic prohibits enabling the engine compression brakes whenever the engine is fueling. This is necessary to prevent possible engine or engine compression brake damage. Therefore, an engine overspeed condition may occur if throttle actuation is continued by an operator even though an engine overspeed threshold has already been reached by the engine.
Overspeed control may be particularly important where travel over different terrain may complicate operation of the vehicle. In particular, if an operator is driving a truck up hill, typically the throttle is being actuated to keep engine speeds and torque at a high level. After cresting the top of the hill, if the operator keeps his foot on the accelerator pedal, engine compression brakes will not enable, since the electronic engine controller inhibits engine brake activation while fueling the engine. Such a controller normally has been programmed into the controller since there are very few times that the operator would want to enable the engine brakes when the driver is requesting more power from the engine. However, after cresting on the top of the hill, the vehicle begins a downward descent and speed control would be desirable. Nevertheless, if the operator keeps his foot on the accelerator pedal, the vehicle will be unable to take advantage of engine braking, the normal resistence to displacement of the pistons in the cylinders, when the fueling level is inadequate to maintain the speed at which the engine is turning.
The present invention overcomes the abovementioned disadvantages by providing an electronic control system for an engine that can detect engine overspeed operation at a level selected to be undesirable and inhibiting response to a request for engine fueling. The response may be a generation of a signal that limits the engine speed below a threshold defined as undesirable. Moreover, the overspeed level may be programmed into the control or otherwise selected as desired to avoid an undesirable absence of engine braking when vehicle speed control is desirable.
In the preferred embodiment, an electronic engine controller, for example, an existing DDEC IV controller, that may be modified to use the existing overspeed digital output, is provided with a control that also has a throttle inhibit to enable the engine compressor brakes when an engine overspeed event occurs. According to the present invention, when the engine speed reaches a programmable overspeed threshold, a digital output is activated, for example, a switch to ground. The digital output is connected to a throttle inhibit digital input of the controller. In the preferred example, grounding the input enables the throttle inhibit function, to disable or override the throttle request being initiated by the operator. Such a control may be useful provided that the other criteria for engine brake operation are all satisfied. Nevertheless, other electronic controllers could be modified to include software logic that allows the engine to ignore fueling requests above a certain threshold engine speed, regardless of accelerator pedal position, thus allowing engine brake activation above a programmable engine speed. Also, a device could send an inhibit fueling message via a digital communication link such as SAE J1939 or SAE J1922 when the accelerator pedal actuation is to be ignored for purposes of engine compression braking.
The present invention will be more clearly understood by reference to the following detailed description of a preferred embodiment when read in conjunction with the accompanying drawing, in which like reference characters refer to like parts throughout the views, and in which:
Engine 10 includes an engine control module (ECM) 14. ECM 14 communicates with various engine sensors and actuators via associated cabling or wires, indicated generally by reference numeral 18, to form a controller 32 to control the engine and equipment 11. In addition, controller 32 communicates with the engine operator using associated lights, switches, displays, and the like as illustrated in greater detail in
Referring now to
Actuators 36 include various vehicle components which are operated via associated control signals from controller 32. As indicated in
Sensors 34 and actuators 36 may be used to communicate status and control information to an engine operator via a console 48. Console 48 may include various switches 50 and 54 in addition to indicators 52. Console 48 is preferably positioned in close proximity to the engine operator, such as in the cab of a vehicle. Indicators 52 may include any of a number of audio and visual indicators such as lights, that may be displayed or illuminated as a response to detection of engine operation in a speed range deemed undesirable, including displays, buzzers, alarms, and the like. Preferably, one or more switches, such as switch 50 and switch 54, are used to request a particular operating mode, such as cruise control or PTO mode, for example.
In one embodiment, controller 32 includes a programmed microprocessing unit 70 in communication with the various sensors 34 and actuators 36 via input/output port 72. As is well known by those of skill in the art, input/output ports 72 provide an interface in terms of processing circuitry to condition the signals, protect controller 32, and provide appropriate signal levels depending on the particular input or output device. Processor 70 communicates with input/output ports 72 using a conventional data/address bus arrangement. Likewise, processor 70 communicates with various types of computer-readable storage media 76 which may include a keep-alive memory (KAM) 78, a read-only memory (ROM) 80, and a random-access memory (RAM) 82. The various types of computer-readable storage media 76 provide short-term and long-term storage of data used by controller 32 to control the engine. Computer-readable storage media 76 may be implemented by any of a number of known physical devices capable of storing data representing instructions executable by microprocessor 70. Such devices may include PROM, EPROM, EEPROM, flash memory, and the like in addition to various magnetic, optical, and combination media capable of temporary and/or permanent data storage.
Computer-readable storage media 76 include data representing program instructions (software), calibrations, operating variables, and the like used in conjunction with associated hardware to control the various systems and subsystems of the engine and/or vehicle. The engine/vehicle control logic is implemented via controller 32 based on the data stored in computer-readable storage media 76 in addition to various other electric and electronic circuits (hardware).
In the preferred embodiment of the present invention, controller 32 includes control logic to detect engine overspeed operation, for example, by comparing sensed, actual engine speed to a programmed threshold engine speed that may be selected as desired. Control logic implemented by controller 32 monitors operating speed of the engine, transmission, or other powertrain connected components. Likewise, the detector 88 determines an indication that the engine speed is above the threshold speed limit. Controller 32 then receives input from sensor 38 that accelerator pedal 39 is engaged by the operator. The controller 32 then automatically adjusts the engine operating mode or powertrain functions to limit operation above the engine speed threshold and control the speed of the vehicle. Of course, depending upon the particular application, one or more thresholds may be selected for monitoring.
As used throughout the description of the invention, a selectable or programmable limit or threshold may be selected by any of a number of individuals via a programming device, such as device 66 selectively connected via an appropriate plug or connector 68 to controller 32. Rather than being primarily controlled by software, the selectable or programmable limit may also be provided by an appropriate hardware circuit having various switches, dials, discrete components and the like. Of course, the selectable or programmable limit may also be changed using a combination of software and hardware without departing from the spirit of the present invention.
As will be appreciated by persons of skill in the art, control logic may be implemented or effected in hardware, software, or a combination of hardware and software. The various functions are preferably effected by a programmed microprocessor, such as included in the DDEC controller manufactured by Detroit Diesel Corporation, Detroit, Mich. Of course, control of the engine/vehicle may include one or more functions implemented by dedicated electric, electronic, or integrated circuits. As will also be appreciated by those of skill in the art, the control logic may be implemented using any of a number of known programming and processing techniques or strategies and is not limited to the order or sequence illustrated or described. For example, interrupt or event driven processing is typically employed in real-time control applications, such as control of an engine or vehicle. Likewise, parallel processing, multi-tasking, or multi-threaded systems and methods may be used to accomplish the objectives, features, and advantages of the present invention. The invention is independent of the particular programming language, operating system, processor, or circuitry used to develop and/or implement the control logic illustrated. Likewise, depending upon the particular programming language and processing strategy, various functions may be performed in the sequence illustrated, at substantially the same time, or in a different sequence while accomplishing the features and advantages of the present invention. The illustrated functions may be modified, or in some cases omitted, without departing from the spirit or scope of the present invention.
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As shown in
It may also be understood that software logic may be modified to allow engine braking at some threshold above rated speed regardless of the throttle position. In addition, a device could send an inhibit fueling message command via digital communication link such as SAE J1939 or J1922.
Having thus described the present invention, many modifications may become apparent to those skilled in the art to which it pertains without departing from the scope and spirit of the present invention as defined in the appended claims.
