This invention relates generally to engine control systems, and more particularly to engine control systems adapted for controlling an engine upon loss of such engine""s primary crankshaft position sensor.
As is known in the art, on modern internal combustion engines, engine speed and position is determined by a sensor reading mechanical features on the rotating crankshaft, often called a crankshaft position sensor (CKP). Upon failure of this sensor or the associated wiring, the electronic system does not have necessary signal information. In many cases, this results in an inability to run the internal combustion engine. In some cases, a second position sensor, like a camshaft position sensor, can be utilized to provide engine operation albeit at a reduced function level.
More particularly, the crankshaft position sensor (CKP) provides highly accurate information to the Powertrain Control Module (PCM) and is utilized by the internal software in providing proper operation of the internal combustion engine. Upon failure of this sensor, the software will either be unable to work, thus disabling engine operation; or, in some systems, the software will provide use of other sensor inputs to run the engine under these different sensor inputs, usually, however, at a reduced function level.
The inventors have recognized a method for correcting for the loss of the primary crankshaft position sensor for a Powertrain control module having a Central Processing Unit (CPU) which includes the use of one or more Time Processing Units (TPUs). Initially, the CPU loads a first, normal engine operating program stored in the CPU memory into the TPU memory. The TPU uses the first computer program to control the engine in the absence of detection of a failure in primary crankshaft position sensor. Upon detection of a failure, the CPU loads a second program stored in the CPU memory into the TPU memory. The TPU executes the second program loaded into the TPU memory to thereby control the engine upon the loss of such engine""s primary crankshaft position sensor.
More particularly some Powertrain Control Modules (PCM) for Internal Combustion Engines utilize Central Processing Unit (CPU) Architectures with Time Processing Units (TPU) which perform key calculation and control functions. These TPUs provide efficient means of performing calculation intensive functions. These TPU units typically contain relative small amounts of RAM space, which limits program size allowable on the TPU. A key feature of the TPU is its proactive approach to handling events and the resulting fine resolution achieved for waveform generation and measurement. The TPU consists of a single microsequencer and dedicated channel hardware (there are 16 channels). The microsequencer prepares the channel-specific hardware to react to possible future events. When a particular event actually occurs, the hardware autonomously performs some action and requests microsequencer servicing. Because the hardware is autonomous, the usual latency penalties associated with an undedicated microsequencer are not incurred. The microsequencer responds to the service request (after servicing any existing requests based on an optimized scheduling mechanism) and prepares the channel hardware for the next event. Further description of a time processor unit (TPU) is in xe2x80x9cTPU Time Processor Unit Reference Materialxe2x80x9d published by Motorola, Inc., 1996 the entire subject matter thereof being incorporated herein by reference.
In some configurations, these TPU segments are used to control Electronic Ignition, Fueling and other functions. These functions often have significant calculation and control requirements and the software size requirements for normal function do not allow sufficient memory size to provide for special functions, like compensating for partial system failure. One situation is to provide continuing operation under system failure conditions, like a crankshaft position sensor failure.
In accordance with the present invention, a method for controlling an internal combustion engine system upon loss of a crankshaft position sensor signal produced by such system is provided. The method includes providing a control module having a central processing unit and a time processor unit associated with such central processing unit. The time processor unit has programmed into it a first code for operating the engine system in the presence of a proper crankshaft position sensor signal. The control module stores a second code for loading into the time processor unit to operate the engine system with the time processor unit upon detection of an improper crankshaft position sensor signal. Initially, the engine system is operated with the time processor unit executing the first code. The method monitors the crankshaft position signal for a fault. Upon detection of the fault, the method loads the second code into the time processor unit and operates the engine system with the time processor unit executing the second code.
In accordance with the present invention, in a normal engine operating mode (i.e., with proper crankshaft position signals), standard engine operating software is loaded to the TPU. In a failure mode management mode, (i.e., upon detection of an improper crankshaft position signals), special compensation software is loaded into and executed by the TPU.
In one embodiment, the engine operator initiates power to the PCM, usually through turning the key in the ignition switch. The PCM loads normal operation software into the necessary TPUs for engine operation (assuming no parameters were noting special software loads needed). The PCM determines the crankshaft position sensor is not providing a proper signal and sets a parameter to indicate the crankshaft position sensor is failed. The operator turns the PCM power xe2x80x9coff xe2x80x9d by turning the ignition key to an xe2x80x9coffxe2x80x9d position. The operator turns the ignition key back xe2x80x9conxe2x80x9d providing the power to the PCM a second time. Upon initialization, the PCM recognizes the crankshaft position sensor (or other system) has failed. The PCM loads special software to the TPU to compensate for the failed sensor (or other system). The engine can then be operated, possibly at a reduced function level.