The present invention is related to the field of over temperature protection for internal combustion engines.
Most, if not all vehicles in production today utilize one or more microprocessors and other digital electronics to control the vehicle""s engine, transmission, brakes, and a variety of other major systems. The microprocessors and other electronics are typically located in one or more housings commonly called electronic control modules (ECM). ECMs are versatile components that can change their behavior and the behavior of the items they are controlling by changing software programs executed by the ECMs. Programmability allows a single ECM design to be adapted to many different types of engines, or transmissions, or braking systems, and so on. Variations in programming allow two otherwise identical systems to exhibit different behavior. For example, two identical engines may have different torque ratings at a given engine RPM due to differences in calibration tables programmed into the ECMs.
Engine protection is an important function often programmed into ECMs. Of particular interest are over temperature conditions during which the engine temperature reaches levels that could be damaging or destructive. Here, the ECM must take some action to increase the cooling rate for the engine and/or decrease the rate at which the engine generates heat. Problems can arise when an increase in the cooling rate takes a considerable time to be effective. The engine temperature may exceed a critical level before the additional cooling can bring the temperature down. On the other hand, decreasing the heat generation rate of the engine may be performed quickly, but it may be contrary to the wishes of the vehicle""s operator.
One method of engine over temperature protection is disclosed U.S. Pat. No. 5,070,832 issued to Hapka et al. on Dec. 10, 1991. Hapka et al. discloses a method that monitors several fluid parameters associated with the engine looking for fault conditions. Typical faults include high fluid temperatures, low fluid levels and low fluid pressures. When fluid parameter faults are detected, an ECM derates the torque and/or speed of the engine based upon the severity and type of faults detected. Performance derating increases linearly as the fluid parameters move farther out of their normal operating ranges. Filtering provides isolation from short fault transients in the fluid parameters that are not severe enough to require engine protection. The Hapka et al. approach is most effective when the engine is operating near or at its rated performance. Here, a slight derating will most likely require the ECM to lower the engine""s actual performance. Performance derating effectiveness drops in scenarios where the engine is operating well below its ratings. In these cases, the derated performance may still be above the engine""s actual performance and thus the ECM is not required to change engines"" operations.
Another engine over temperature protection approach is to reduce the torque controlling signal or signals being used to control the engine. In this approach, the ECM records the values of the torque controlling signals at the beginning of an over temperature condition. These signals are then reduced as a linear function of temperature to cause the torque and heat being generated by the engine to reduce. In this approach, the ECM will always take some action that will promote the lowering of the engine""s temperature.
A consequence of both engine protection approaches is that the vehicle""s driver may become aware of the protective action due to a reduction in the vehicle""s speed and/or the illumination of a notification lamp. When this happens, the driver may attempt to compensate by increasing the throttle input manually. This usually does not have the desired effect since the ECM is executing the engine protection routine. As a result, the driver typically concludes that the engine has somehow failed. While an engine failure is one possible explanation for the over temperature condition, another explanation is that the engine is being operated outside its designed operating environment. For example, an engine over temperature condition may be caused by the vehicle moving up a steep grade high in the mountains carrying a heavy load on an unusually hot day. In this example, there may not be sufficient air flow past the radiator to cool the engine adequately.
The present invention is method of operation to protect an engine during an over temperature condition, an information recording medium including a computer program implementing the method, and an electronic control module performing the method. Onset of the protection is made gradual to minimize the impact of the protection on overall engine performance. The rate of protection then increases if the engine temperature continues to increase.
An operating torque signal representative of a torque being generated by the engine is recorded to produce a recorded torque value in response to a temperature signal representative of a temperature of the engine exceeding a protection temperature threshold. The torque being generated by the engine is then reduced as a nonlinear function of the temperature signal and the recorded torque value to promote lowering of the temperature of the engine. A notification indicator and a warning indicator are activated if the engine temperature exceeds a notification temperature threshold and a warning temperature threshold respectively. The torque reduction may be limited to no less than a fixed percentage of the recorded torque value, or to no less than a minimum absolute torque value, whichever is greater.
Diagnostic fault logging may be provided to log the engine temperature exceeding the protection, notification and warning temperature thresholds. Fault broadcasting may also be provided to notify other control modules and systems that the engine temperature has exceeded the notification and then the warning temperature thresholds.
Accordingly, it is an object of the present invention to provide a method and apparatus for protecting and engine during an over temperature condition implementing a nonlinear response to the engine temperature.
These and other objects, features and advantages will be readily apparent upon consideration of the following detailed description in conjunction with the accompanying drawings.