Patent Application
20200291877
The present disclosure relates to vehicle active thermal control systems for tracking and improving efficiency.
Automobile vehicle engines commonly have pre-programmed operating condition ranges that improve fuel and operating efficiency. Efficiency can be increased in two ways, by increasing a peak combustion temperature, or by lowering an exhaust temperature. Vehicle engines have their highest temperature conditions occurring local to the cylinder heads. Peak combustion temperature can be increased until engine “knock” begins to occur. To protect the engine against the occurrence of engine knock manufacturers commonly predetermine a maximum allowable cylinder head temperature that prevents engine knock and select an engine coolant temperature set point which prevents local coolant boiling in the coolant jacket surrounding the cylinders and limits cylinder head temperature to prevent engine knock at vehicle operating conditions. This approach protects the engine for maximum engine and ambient conditions such as for operation in high temperature environments, but at the expense of maximum fuel efficiency which could be obtained by changing the coolant set point for operation during normal or cold ambient driving conditions.
Thus, while current vehicle engine control systems achieve their intended purpose, there is a need for a new and improved system and method for controlling vehicle engine efficiency.
According to several aspects, a method for controlling an engine thermal target setpoint includes: identifying in a first step an initial NOx integral at a calculated initial cylinder wall temperature and a thermal set point of an engine coolant; initiating a command in a second step to change the cylinder wall temperature and to change the thermal set point of the engine coolant; and creating in a third step a new NOx integral at a new cylinder wall temperature and a modified thermal set point of the engine coolant.
In another aspect of the present disclosure, the method includes comparing in a fourth step: is (the new NOx integral minus the initial NOx integral) greater than a predefined minimum threshold.
In another aspect of the present disclosure, the method includes comparing in the fourth step: is (the new NOx integral minus the initial NOx integral) less than a predefined maximum threshold.
In another aspect of the present disclosure, the method includes generating a command signal to decrease the thermal set point of the engine coolant if the response to the comparisons performed in the fourth step is YES.
In another aspect of the present disclosure, the method includes generating a command signal to increase the thermal set point of the engine coolant if the response to the comparisons performed in the fourth step is NO.
In another aspect of the present disclosure, the method includes limiting the predefined maximum threshold to prevent localized boiling of the engine coolant in a cylinder cooling jacket and knock of an engine.
In another aspect of the present disclosure, the method includes incorporating an output signal from a NOx sensor to calculate the initial cylinder wall temperature, the initial NOx integral, and the new NOx integral.
In another aspect of the present disclosure, the method includes estimating a NOx level output from an engine to calculate the initial cylinder wall temperature.
In another aspect of the present disclosure, the method includes tracking NOx changes and applying the NOx changes to data saved in a memory to calculate cylinder wall maximum temperatures.
In another aspect of the present disclosure, the method includes generating predicted ideal cylinder wall temperature targets based on the integrated NOx changes defined as differences between the new NOx integral and the initial NOx integral.
According to several aspects, a method for controlling an engine thermal target setpoint, includes: identifying in a first step an initial NOx integral at an initial calculated cylinder wall temperature and a thermal set point of an engine coolant; initiating a command in a second step to change the initial cylinder wall temperature and to change the thermal set point of the engine coolant; creating in a third step a new NOx integral at a new cylinder wall temperature and a modified thermal set point of the engine coolant; and comparing in a fourth step: is (the new NOx integral minus the initial NOx integral) greater than a predefined minimum threshold; and is (the new NOx integral minus the initial NOx integral) less than a predefined maximum threshold.
In another aspect of the present disclosure, the method further includes calculating the initial cylinder wall temperature using NOx data saved in a memory.
In another aspect of the present disclosure, the method further includes predicting the modified thermal set point using NOx data from the memory.
In another aspect of the present disclosure, the method further includes calculating the initial cylinder wall temperature, the initial NOx integral, the new NOx integral and the modified thermal set point using output signals from a NOx sensor and NOx data saved in a memory.
In another aspect of the present disclosure, the initial NOx integral and the new NOx integral are directly proportional to a peak cylinder wall temperature.
In another aspect of the present disclosure, the method further includes repeating the first through the fourth steps to identify if further improvement in fuel economy is available by increasing a cylinder wall temperature.
In another aspect of the present disclosure, the method further includes repeating the first through the fourth steps to identify if the cylinder wall temperature has reached a maximum allowable cylinder wall temperature based on a NOx production of an engine.
According to several aspects, a system for controlling an engine thermal target setpoint includes an initial NOx integral determined at a calculated initial cylinder wall temperature and a thermal set point of an engine coolant. A command is generated to change the cylinder wall temperature and to change the thermal set point of the engine coolant. A new NOx integral at a new cylinder wall temperature and a modified thermal set point of the engine coolant are created following the command. A first determination identifies if the new NOx integral minus the initial NOx integral is greater than a predefined minimum threshold; and a second determination identifies if the new NOx integral minus the initial NOx integral is less than a predefined maximum threshold.
In another aspect of the present disclosure, a NOx sensor generates an output signal defining a NOx level in an engine exhaust, the initial NOx integral, and the new NOx integral.
In another aspect of the present disclosure, an engine controller calculates an estimated NOx output using data saved in a memory.
Further areas of applicability will become apparent from the description provided herein. It should be understood that the description and specific examples are intended for purposes of illustration only and are not intended to limit the scope of the present disclosure.
The drawings described herein are for illustration purposes only and are not intended to limit the scope of the present disclosure in any way.
The following description is merely exemplary in nature and is not intended to limit the present disclosure, application, or uses.
Referring to
Exhaust gas is discharged from the cylinders 14 into an exhaust manifold 24 which is delivered into an exhaust line 26. A turbocharger 28 can also be connected to the exhaust manifold 24 as is known, which provides boosted pressure via a boost pressure line 30 to a charge air cooler 32, which cools the gas discharged by the turbocharger 28 prior to being delivered into the intake manifold 22 to boost the air pressure in the intake manifold 22.
A control device such as an engine controller 34 receives signals from multiple sources and outputs control signals which control operation of the engine 12. One of the signal sources for the engine controller 34 can be a nitrogen oxide (NOx) sensor 36. Engine NOx output passing through the exhaust line 26 is sensed by the NOx sensor 36 which converts NOx output to an electrical output signal for transmission to the engine controller 34. If the NOx sensor 36 is not available or in addition to the signal output from the NOx sensor 36 the engine controller 34 can also calculate an estimated NOx output using data saved in a memory 37 such as one or more NOx lookup tables. The engine controller 34 or a similar controller is used to control delivery of an engine coolant from a coolant system 38 of known design to coolant jackets 40 of the cylinders 14. As will be described in greater detail in reference to
According to several aspects, the NOx sensor 36 is introduced into the engine exhaust line 26 and produces signals which correlate to engine output conditions at a peak cylinder temperature. NOx sensor 36 output signals are therefore converted in the engine controller 34 to determine peak cylinder temperatures. The peak cylinder temperatures are applied to determine if an adjustment to the set point temperature for the thermal system wall temperature can be made to maximize efficiency under multiple different operating conditions. For example, by utilizing an output from the NOx sensor 36 a determination can be performed if peak cylinder temperature is rising or if the thermal benefits achievable by changing the set point temperature of the engine coolant which allow higher cylinder temperatures to minimize or eliminating engine knock or allowing localized boiling of the engine coolant have been maximized. If the NOx sensor 36 is not available, the signals produced by the NOx sensor 36 can also be simulated using a NOx sensor model using lookup table data saved in a memory.
Referring to
If the response to queries in step 50 is YES, in a step 52 a command signal is generated to decrease the thermal set point of the engine coolant. This decrease in the thermal set point of the engine coolant reduces the cylinder wall temperature to prevent engine knock and therefore to protect system hardware.
If the response to queries in step 50 is NO, in a step 54 a command signal is generated to increase the thermal set point of the engine coolant. This increase in the thermal set point of the engine coolant increases the cylinder wall temperature to increase fuel economy while minimizing the potential for engine knock and localized boiling of the engine coolant in the coolant jackets 40.
During vehicle engine operation the algorithm 42 continuously loops on a predetermined time interval. The algorithm 42 identifies if further improvement in fuel economy is available by increasing cylinder wall temperature, or if cylinder wall temperature has reached a maximum allowable wall temperature based on NOx production requiring additional engine coolant flow to reduce a temperature of the coolant in the coolant jackets 40.
Referring to
Referring to
To maximize thermal efficiency NOx production is used with the engine thermal target setpoint system 10 because NOx production of the engine 12 is a strong function of peak cylinder wall temperature. This relationship has been found to be directly proportional. For example, for every approximate +50C temperature increase in cylinder wall temperature NOx production is doubled. By tracking NOx changes the engine thermal target setpoint system 10 can calculate corresponding cylinder wall maximum temperatures. Predicted ideal cylinder wall temperature targets 78 can thereby be determined based on the integrated NOx changes and cylinder wall temperatures and can be controlled by changing coolant flow to the cylinder walls. The predicted ideal cylinder wall temperature targets 78 are based on integrated NOx changes defined as differences between the new NOx integral and the initial NOx integral.
The engine thermal target setpoint system 10 provides the ability to read or predict NOx relative to engine output conditions. Either relative changes can be predicted using data saved in a memory such as in lookup tables of the engine controller 34, or measured changes sensed by the NOx sensor 36 can be used. The engine thermal target setpoint system 10 is not focused on an absolute accuracy of the NOx sensor 36 because the trend or change in cylinder wall temperature is also related to a type of fuel used such as the fuel octane rating and the type and amount of fuel additives such as ethanol fuel blend, plus vehicle ambient conditions. The engine thermal target setpoint system 10 therefore uses an algorithm to determine and change cylinder wall temperature set points based on the above conditions. The system 10 also permits predictions of engine fuel efficiency available based on Carnot principles.
An engine thermal target setpoint system of the present disclosure offers several advantages. By integrating NOx values at various engine output conditions and comparing to actual or predicted cylinder wall temperatures, active thermal controls can be adjusted to increase engine efficiency while minimizing the potential for engine knock and localized coolant boiling at the cylinder walls.
The description of the present disclosure is merely exemplary in nature and variations that do not depart from the gist of the present disclosure are intended to be within the scope of the present disclosure. Such variations are not to be regarded as a departure from the spirit and scope of the present disclosure.
