Internal-combustion engines – Combustion chamber means having fuel injection only – Having a particular relationship between injection and...
Reexamination Certificate
1999-03-05
2001-06-19
Dolinar, Andrew M. (Department: 3747)
Internal-combustion engines
Combustion chamber means having fuel injection only
Having a particular relationship between injection and...
C123S295000, C123S350000, C701S107000
Reexamination Certificate
active
06247445
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to a method for operating an internal combustion engine, in particular of a motor vehicle, in which fuel is injected either in a first operating mode during a compression phase, or in a second operating mode during an intake phase, directly into a combustion chamber. In both operating modes, the fuel mass injected into the combustion chamber is controlled and/or regulated as a function, among other things, of a calculated reference torque to be delivered by the internal combustion engine. The present invention also relates to an internal combustion engine, in particular for a motor vehicle, having an injection valve with which fuel can be injected either in a first operating mode during a compression phase, or in a second operating mode during an intake phase, directly into a combustion chamber. The internal combustion engine includes a control device for controlling and/or regulating the fuel mass injected into the combustion chamber in the two operating modes, as a function, inter alia, of a calculated reference torque to be delivered by the internal combustion engine.
BACKGROUND INFORMATION
Conventional systems for a direct injection of fuel into the combustion chamber of an internal combustion engine are commonly known. A distinction is made in this context between “stratified” mode as a first operating mode, and “homogeneous” mode as a second operating mode. Stratified mode is used in particular at lower loads, while homogeneous mode is utilized when larger loads are present at the internal combustion engine. In stratified mode, the fuel is injected during the compression phase of the internal combustion engine into the combustion chamber, specifically into the immediate vicinity of a spark plug therein. The result is that uniform distribution of the fuel in the combustion chamber can no longer occur. The advantage of stratified mode is that the smaller loads that are present can be handled by the internal combustion engine with a very small fuel mass. Stratified mode is not sufficient, however, for greater loads. In the homogeneous mode provided for such greater loads, the fuel is injected during the intake phase of the internal combustion engine, so that turbulent flow and thus distribution of the fuel in the combustion chamber can still readily occur. To this extent, homogeneous mode corresponds approximately to the operation of internal combustion engines in which fuel is injected conventionally into the intake duct.
In both operating modes, i.e. in stratified and in homogeneous mode, the fuel mass to be injected is controlled and/or regulated by a control device, as a function of a plurality of input variables, to a value that is optimal in terms of fuel economy, emissions reduction, and the like. This control and/or regulation depends, among other things, on a reference torque that is calculated by the control device. The reference torque represents the total torque to be delivered by the internal combustion engine, i.e. the torque which the internal combustion engine is intended to generate. This reference torque is made up, among other things, of the torque requested by the driver and optionally of other torque requirements, for example of a climate-control system or the like. The torque requested by the driver is derived from the position of the accelerator pedal actuated by the driver.
It is possible, however, that a fault may occur in the calculation, by the control device, of the reference torque from the aforesaid input variables. This may involve a fault of a sensor and/or of the control device and/or the like. In particular, it may involve a software fault in the control device which, because the fault occurs infrequently, has not hitherto been detected.
It is the object of the present invention to create a method with which a fault in the calculation of the reference torque can be detected.
SUMMARY OF THE INVENTION
According to the present invention this object is achieved, in a method and in an internal combustion engine, in that a true torque delivered by the internal combustion engine and a permissible torque are determined; and the true torque is compared to the permissible torque.
In other words, a comparison is made between the delivered true torque as determined, and a permissible torque as determined. The true torque and the permissible torque are independent of the (possibly erroneously calculated) reference torque. For this reason, a fault in the reference torque cannot affect the aforesaid comparison. A decision is then made as a function of the comparison as to whether or not the reference torque is erroneous.
The method according to the present invention thus makes it possible to check or monitor the reference torque calculated by the control device. It is possible to ascertain, by way of the comparison, whether the reference torque has been correctly or erroneously calculated by the control device. This check, and the detection thereby achievable of a fault in the calculation of the reference torque, can prevent a resulting erroneous injection of fuel into the combustion chambers of the internal combustion engine. This directly contributes to fuel economy and emissions reduction, and in general to better operation of the internal combustion engine.
It is also advantageous if a particular function is started if the true torque is greater than the permissible torque. The permissible torque thus represents a maximum value which must not be exceeded by the true torque per se. If, however, the true torque is greater than the aforesaid maximum value, the special function then, for example, starts a fault routine or the like which either causes the control device to attempt to correct the fault by way of corresponding corrections, or makes the driver or a mechanic aware of the fault.
In an another embodiment of the present invention, the true torque is determined from the combusted fuel mass. This makes possible a very accurate calculation of the true torque. The combusted fuel mass can be derived, for example, from the signals activating the injection valves, or can be determined by way of other operating parameters of the internal combustion engine.
In another embodiment of the present invention, the true torque is determined from the combusted oxygen mass. In this fashion too, it is possible to calculate the true torque very accurately. From the combusted oxygen mass that is then available, conclusions can then be drawn as to the combusted fuel mass and thus in turn as to the true torque.
In another embodiment of the present invention, the combusted oxygen mass is determined from the infed fresh air and the oxygen remaining in the exhaust gas. In particular, the difference is determined between the oxygen content of the infed fresh air and the oxygen mass remaining in the exhaust gas. This represents a simple yet very accurate and effective way of calculating the combusted oxygen mass and thus ultimately the true torque of the internal combustion engine.
It is advantageous if the fresh air is measured by an air mass sensor, and the oxygen remaining in the exhaust gas by a lambda sensor. The air mass sensor and lambda sensor are usually already provided on the internal combustion engine for other purposes, so that to that extent no additional components are necessary in order to check or monitor the reference torque as defined by the present invention.
In another embodiment of the present invention, exhaust gas recirculation is taken into consideration in determining the combusted oxygen mass. In other words, consideration is given to the fact that the exhaust gas fed into to the combustion chambers by recirculation has a lower oxygen content than the fresh air fed directly into the combustion chambers; and that because of the recirculated exhaust gas, the proportion of infed fresh air is lower. This in turn offers the advantage that the tolerance of the air mass sensor measuring the infed fresh air also plays a lesser role.
In another embodiment of the present invention, the permissible torque
Dolinar Andrew M.
Kenyon & Kenyon
Robert & Bosch GmbH
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