Internal-combustion engines – Poppet valve operating mechanism – With means for varying timing
Reexamination Certificate
1999-12-10
2001-04-10
Lo, Weilun (Department: 3748)
Internal-combustion engines
Poppet valve operating mechanism
With means for varying timing
C123S090110, C073S116070, C073S117020, C073S118040
Reexamination Certificate
active
06213068
ABSTRACT:
FIELD OF THE INVENTION
The invention relates to a diagnosis of a variable control of the gas exchange in an internal combustion engine.
BACKGROUND OF THE INVENTION
The term gas exchange characterizes the periodic change of the cylinder charge, that is, the discharge of exhaust gas and the inflow into the combustion chamber of air or air/fuel mixture. In conventional internal combustion engines, the control of the gas exchange takes place via resiliently-biased valves which are opened by a camshaft. The opening function is a time-dependent function, that is, the start, duration and extent of the opening are determined by the form of the camshaft. The opening function can therefore be precisely fixed by the shape of the camshaft but is not variable.
Additional systems are known for controlling the exchange of gas with a variable opening function. International patent publication WO 91/08384 corresponds to U.S. Pat. No. 4,957,074 and discloses an electromagnetically controlled and hydraulically actuated valve having a variable opening function. German patent publication 195 01 386 corresponds to U.S. Pat. No. 5,588,411 and discloses a variable valve control wherein the opening function of the gas-exchange valve is determined by an opening camshaft and a closing camshaft. The opening function can be varied within wide limits via a change of the phase shift between the shafts rotating at the same rotational frequency.
The operability of the variable valve control or the operability of the change of the opening function is relevant for the emission of the exhaust gas and must therefore be monitored.
SUMMARY OF THE INVENTION
It is an object of the invention to provide a method of monitoring the variable valve control without additional sensors. More specifically, it is an object of the invention to provide such a method utilizing already available sensors which are provided for other purposes. Those sensors which are anyway already available detect the air mass inducted by the engine and are sensors for the position of the throttle flap in the intake manifold and, if required, for the pressure in the intake manifold.
The method of the invention is for checking the operability of a variable valve control in an internal combustion engine having an intake manifold and wherein the state of the variable valve control contributes to determining the combustion chamber charge. The method includes the steps of: providing a first signal indicative of the air mass actually drawn in by the engine via the intake manifold; forming a primary signal (HLS) for the combustion chamber charge from the first signal; providing a second signal formed from a desired value for the state of the variable valve control and at least one of the following: the position of a throttle flap, the pressure in the intake manifold and the rpm of the engine; forming an ancillary signal (NLS) for the combustion chamber charge from the second signal; comparing the primary and ancillary signals (HLS, NLS) and forming an index for the deviation of the primary and ancillary signals (HLS, NLS) from each other; and, outputting and/or storing a fault signal when the index exceeds a predetermined value.
The invention is based on the consideration that a change of the opening function of the inlet valve influences the throttling of the engine directly at the inlet valves. Throttling, in this context, is understood to mean that the gas quantity, which flows via the valve, becomes less with decreasing valve stroke and with decreasing duration of opening. For the same throttle flap angle, the cylinder charge is thereby dependent upon the throttle action of the inlet valves and therefore upon the opening function. The cylinder charge can also be characterized as load and can be computed from the signal of an air mass sensor. Known air mass sensors are hot wires or hot-film air mass sensors. These sensors supply a so-called primary load signal HLS which is derived from the inducted air mass. A further index for the cylinder charge can be derived from the opening angle a of a throttle flap in the intake manifold. This additional index is identified in the following as an ancillary load signal NLS.
In contrast to the primary load signal, the ancillary load signal is dependent upon the opening function of the inlet valves. If the provided opening function does not develop, then the ancillary load signal is burdened with an error. An essential element of the invention is the evaluation of the operability of the variable valve control on the basis of a comparison of the primary and ancillary load signals.
This affords the advantage that no additional actuators or sensors are needed for the diagnosis. A further advantage is that the diagnosis is possible in the normal operation of the engine. The only slight complexity as to additional software is also advantageous because the primary load signal and the ancillary load signal are already present.
An embodiment of the invention includes a lambda control in the diagnosis, with this lambda control being individual for a cylinder bank. This permits a determination as to whether both cylinder banks or only one cylinder bank are/is affected by the malfunction and, furthermore, the affected cylinder bank can be identified.
REFERENCES:
patent: 4957074 (1990-09-01), Weissler, II et al.
patent: 5549080 (1996-08-01), Uchikawa
patent: 5588411 (1996-12-01), Kreuter et al.
patent: 5644073 (1997-07-01), Matsuno et al.
patent: 5979378 (1999-11-01), Matsuno et al.
patent: 6050250 (2000-04-01), Kerkau
Lo Weilun
Ottesen Walter
Robert & Bosch GmbH
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