This application is the US National Stage of International Application No. PCT/EP2005/051438, filed Mar. 30, 2005 and claims the benefit thereof. The International Application claims the benefits of German Patent application No. 10 2004 030 604.4 filed Jun. 24, 2004. All of the applications are incorporated by reference herein in their entirety.
The present invention relates to a method for determining the air mass in a cylinder of an internal combustion engine with a supercharging device and a facility for variable activation of the valve overlap of the gas exchange valves.
A cylinder air charge controller is known from DE 100 50 059 A1, which adjusts inlet and outlet valves as a function of a required torque. When a turbocharger is used, it is proposed that the control device for inlet and outlet valves should be opened at the same time to prevent the delay in the torque increase, such that where there is a positive pressure difference between the intake and exhaust gas sides, there is a purging of intake air to the exhaust gas side.
A method for controlling an engine is known from DE 100 51 416 A1, which has an electronically controlled inlet and outlet device. To change the air/fuel ratio in the individual cylinders quickly, the outlet regulator is used to control the air flow from the intake manifold into the cylinder.
An engine control system for a direct injection unit with variable valve control time is known from DE 100 51 425 A1, in which fresh air charging into the cylinder is controlled more rapidly with the aid of a cam controller. The method also includes changing the air/fuel ratio in the cylinder and changes the activation of the outlet control device accordingly. A manifold pressure sensor is provided to compensate for incorrect calculations and calculates a pressure error from the difference between the determined manifold pressure and the current manifold pressure.
A direct-injection internal combustion engine with a turbocharger to reduce consumption, particularly in full-load operation is known from EP 1 243 779 A2. To prevent knocking noises, residual gas is purged from the cylinder, in that the gas exchange valves are opened at the same time.
The object of the invention is to provide a method for determining the air mass in a cylinder of an internal combustion engine, which determines the air mass available to the cylinder reliably using simple means.
According to the invention the object is achieved by a method with the features from the claims. Advantageous embodiments are set out in the subclaims.
The inventive method relates to internal combustion engines with a supercharging device, for example an exhaust gas turbocharger, and a facility for variable activation of a valve overlap of the gas exchange valves. The inventive method operates with at least two characteristic curves. The first characteristic curve shows the air mass in the cylinder as the first reference characteristic curve, describing a linear relationship between the air mass in the cylinder and the pressure in the intake pipe as a function of the operating conditions. If the intake pipe pressure exceeds the exhaust gas counterpressure, a value for the trapping efficiency is determined based on a second characteristic curve and used to correct the value of the air mass from the reference characteristic curve. With the inventive method the air mass in the cylinder is described by a linear relationship between the air mass and the pressure in the intake duct. The air values are corrected with the aid of the trapping efficiency [lacuna] purging, in other words in the region where the intake pressure is greater than the exhaust gas counterpressure.
The trapping efficiency (TE) is preferably defined as follows:
where mcyl is the air mass remaining in the cylinder after the charge exchange and meng is the total air mass leaving the cylinder during the charge exchange. The ratio of these air masses is particularly suitable for characterizing the purge effect in the cylinder. The value from the reference characteristic curve is corrected by multiplication.
In a preferred development of the inventive method, if the intake pipe pressure is less than or equal to the exhaust gas counterpressure, the value of the air mass from the reference characteristic curve is corrected using a value for the residual gas remaining in the combustion chamber. For example the air mass is defined for the residual gas in a characteristic curve as a function of operating conditions over the pressure in the intake duct, such that the value for the residual gas is subtracted from the reference characteristic curve to correct the value. The characteristic curve for the air mass of the residual gas preferably runs below a predetermined pressure value in a manner that is essentially proportional to the intake pipe pressure.
In a preferred development at least one of the additional operating conditions, of which the characteristic curve for the trapping efficiency and/or the residual gas is a function, is selected from the following group:
In a particularly preferred embodiment the value for the trapping efficiency is forwarded to a control unit for calculation of the torque and/or ignition correction. It has proven particularly advantageous for the value for the air mass in the cylinder and the correction value defined by purging to be forwarded separately to lower-order control units, instead of a corrected value for the air mass in the cylinder directly.
The inventive method is described in more detail below with reference to two figures, in which:
The fresh air enters the inner chamber 24 of the cylinder by way of the inlet valve 22. The cylinder 26 is illustrated schematically and has a piston 28 with a connecting rod 30, which drives the crankshaft 32. The rotation speed of the crankshaft is captured by a speed sensor 34.
Fuel injection is not shown in further detail in the figures. The injected fuel is ignited by way of the ignition facility 36. After ignition the residual gas is released by way of the outlet valve 38 into the exhaust gas duct 40. A lambda probe 42 measures the oxygen contained in the exhaust gas in the exhaust gas duct.
The internal combustion engine is controlled by way of an engine controller 44, at which the rotation speed N, the throttle valve angle αDK, the oxygen content λAV and the ambient temperature TAL of the fresh air taken in are for example present as input variables. The measured value for the fresh air taken in dmHFN/dt is also present at the engine controller 44.
In the interval A a value 48 for the residual gas remaining in the cylinder is subtracted from the standard absorption characteristic curve 46. As well as subtraction, it is of course also possible to consider a multiplying factor.
In the interval B the mass of air remaining in the cylinder is above the standard absorption characteristic curve 46. Above a critical value P2, the values of the air mass 52 here have an essentially linear pattern, parallel to the standard absorption characteristic curve 46. The increase 54 due to the air mass remaining in the combustion chamber as a result of purging can be different from the air mass occurring in the interval A, which lowers the standard absorption characteristic curve 46.
In the transition area between P1 and P2 the corrected curve has an essentially non-linear, S-shaped pattern.
In a further embodiment of the invention the trapping efficiency is recorded by way of characteristic maps as a function of the position of the valve drive, the engine speed, the intake pipe pressure and the exhaust gas counterpressure. Depending on the embodiment, the trapping efficiency and then the exhaust gas counterpressure may or may not be taken into account during the determination. In one specific embodiment the trapping efficiency (EFF_TRAP) is a function of the engine speed N, the valve overlap VO, the exhaust gas counterpressure PRS_EX, the intake pipe pressure MAP and a selector switch LC_PRS_EX_SCAV_CCC_ENA, which indicates whether the exhaust gas counterpressure is included in the calculation.
Number | Date | Country | Kind |
---|---|---|---|
10 2004 030 604 | Jun 2004 | DE | national |
Filing Document | Filing Date | Country | Kind | 371c Date |
---|---|---|---|---|
PCT/EP2005/051438 | 3/30/2005 | WO | 00 | 12/12/2006 |
Publishing Document | Publishing Date | Country | Kind |
---|---|---|---|
WO2006/000474 | 1/5/2006 | WO | A |
Number | Name | Date | Kind |
---|---|---|---|
4269156 | Drellishak | May 1981 | A |
4404946 | Hoard et al. | Sep 1983 | A |
4941448 | Nakaniwa et al. | Jul 1990 | A |
6675579 | Yang | Jan 2004 | B1 |
6840237 | Strom et al. | Jan 2005 | B2 |
20070062490 | Yang | Mar 2007 | A1 |
Number | Date | Country |
---|---|---|
43 25 902 | Feb 1995 | DE |
100 51 416 | May 2001 | DE |
100 51 425 | May 2001 | DE |
100 50 059 | Jun 2001 | DE |
102 59 052 | Apr 2004 | DE |
103 16 291 | Nov 2004 | DE |
10 2004 050 059 | Apr 2006 | DE |
0 651 149 | May 1995 | EP |
1 041 264 | Oct 2000 | EP |
1 231 372 | Aug 2002 | EP |
1 243 779 | Sep 2002 | EP |
Number | Date | Country | |
---|---|---|---|
20070227500 A1 | Oct 2007 | US |