EP3635231A1

EP3635231A1 - Checking the plausibility of an air mass flow meter

Info

Publication number: EP3635231A1
Application number: EP18727295.0A
Authority: EP
Inventors: Michael Schenk; Peter Baeuerle
Original assignee: Robert Bosch GmbH
Current assignee: Robert Bosch GmbH
Priority date: 2017-06-07
Filing date: 2018-05-28
Publication date: 2020-04-15
Also published as: WO2018224342A1; DE102017209559A1; CN110719993A; CN110719993B

Abstract

The invention relates to a method for operating an internal combustion engine (1), wherein: the mass flow m_A of the drawn-in combustion air (11) is measured by an air mass flow meter; a pressure-based air mass flow meter (13) is selected; the plausibility is checked (140) for the value for m_A with respect to the mass flow m_S flowing through an intake pipe (15) connected between the air mass flow meter (13) and at least one combustion chamber (20) of the internal combustion engine (1); the mass flow ms is determined in an operating state where a mass flow m_R of exhaust gas (12) is returned to the intake pipe (15); and additionally the mass flow m_R is determined (130). The invention further relates to an air supply system for an internal combustion engine (1), comprising: a turbocharger (26); an air mass flow meter (13) arranged after the turbocharger (26) in the direction of flow; a throttle valve (14) arranged after the air mass flow meter (13) in the direction of flow; and an intake pipe (15) arranged after the throttle valve (14) in the direction of flow and connected upstream of a combustion chamber (20) of the internal combustion engine (1), wherein an exhaust gas return line (28) for exhaust gas (12) from the internal combustion engine (1) opens into the intake pipe (15), the air mass flow meter (13) being a pressure-based air mass flow meter (13) and being provided as the single sensor for measuring the charge pressure and charge air temperature. The invention also relates to an associated computer program product.

Description

description

Title:

Plausibility check of an air mass meter

The present invention relates to a method for operating a

Internal combustion engine, in which a malfunction of an air mass meter can be detected, as well as a pre-equipped for this purpose air supply system for an internal combustion engine.

State of the art

Air mass meters are used in the intake tract of internal combustion engines in order to ensure an optimum degree of filling of the combustion chamber and thus optimum combustion. The output of a gasoline engine power is proportional to the intake air mass flow. The correct measurement of the air mass flow is safety relevant. It is therefore required by law that the correct functioning of the air mass meter is monitored.

It is known from US Pat. No. 5,291,803 A, DE 199 46 874 A1 and DE 10 2010 044 164 A1 to plausibilize the air mass flow determined by the air mass meter with a comparison value obtained from other sensors independent of the air mass meter , If the air mass flow deviates too far from the reference value, this can be taken as an indication that there is an error.

Disclosure of the invention

In the context of the invention, a method for operating a

Internal combustion engine developed. The mass flow ΓΤΙΑ of the

sucked combustion air measured by an air mass meter. According to the invention, a pressure-based air mass meter is selected. The value for [TIA is plausibilized against the mass flow ms flowing through a suction pipe connected between the air mass meter and at least one combustion chamber of the internal combustion engine. In this case, the mass flow ms is determined in an operating state in which a mass flow rriR of exhaust gas is recirculated into the intake manifold, wherein the mass flow rriR is additionally determined.

It has been recognized that regardless of the position of a throttle located between the air mass meter and the intake manifold, the mass flow ms should nominally equal the sum of the mass flow ΓΤΙΑ and the recirculated mass flow rriR of exhaust gas. It was further recognized that both the mass flow ms flowing through the intake manifold and the mass flow rriR of exhaust gas can be derived from the quantities supplied by standard sensors in the internal combustion engine at least in a sufficient accuracy for plausibility. Therefore, it is possible to dispense with redundant sensors. The requirement to monitor the correct functioning of the air mass meter can thus be met with little effort.

For example, in the prior art, the pressure and temperature of the air before relaxation by the throttle valve were measured with a boost pressure sensor, and the expansion was over

Throttle equation models. By measuring the intake manifold pressure, the mass flow through the throttle could then be determined as a comparison value for ΓΤΙΑ. In contrast, the plausibility check according to the invention has the advantage that the boost pressure sensor is unnecessary and accordingly costs can be saved.

This is particularly advantageous in combination with a pressure-based air mass meter, for example of the type PFM (Pressure-based Flow Meter). Such an air mass meter measures the static pressure as a reference pressure as well as a pressure difference caused by the mass flow and also the temperature of the air. Therefore, it is a comparatively Complex sensor, which can also take over the function of the boost pressure sensor, because the static pressure corresponds to the boost pressure, and the temperature corresponds to the charge air temperature. Of course, an additional existing boost pressure sensor then plausibility of the

Serve air mass meter. For the exclusive use as such a control body, however, a boost pressure sensor is too expensive.

Instead of determining the mass flow rriR of recirculated exhaust gas, one could in principle set it to zero by temporarily deactivating the exhaust gas recirculation. However, this has over the possible according to the invention

Plausibility check even with active exhaust gas recirculation significant disadvantages. Exhaust gas recirculation can not be closed at every operating point of the engine, especially in the case of natural gas engines for commercial vehicles, since it mainly serves there to reduce the combustion chamber or engine outlet temperature and is necessary for the protection of turbochargers and other components.

Operating conditions in which the exhaust gas recirculation is temporarily unnecessary, sometimes occur in driving too rarely. To the prescribed

Plausibilisierung the air masses perform meter, it may then be necessary to temporarily force an operating condition in which the exhaust gas recirculation can be temporarily disabled. This may mean, for example, that the engine torque must be reduced in order to avoid overheating of the internal combustion engine or the exhaust line. On the one hand, this can be perceived as unpleasant by the driver, because at times not the full requested engine torque is available. On the other hand, with deactivated exhaust gas recirculation possibly also an adjustment of the ignition angle in the direction of late required, which the efficiency of

Combustion deteriorates and increases fuel consumption.

In a particularly advantageous embodiment of the invention is the

Mass flow ms determined from the air mass in the combustion chamber and the speed n of the internal combustion engine. The mass flow ms can, for example, according to the formula

Pc - ^v cn ^■ F {n)

Rc - ^T c

be determined. Here, the fraction indicates the air mass in the combustion chamber under the approximation that the air is treated as an ideal gas, pc, Vc and Tc Accordingly, the pressure, volume and temperature of the air in the combustion chamber, and Rc is the specific gas constant of the air in the combustion chamber, n is the engine speed, and F (n) is dependent on the engine speed

Multiplication factor.

The determination of pc, Vc and Tc is particularly easy at a time when an intake valve of the combustion chamber is opened. Vc then corresponds to the effective displacement of the internal combustion engine, pc corresponds approximately to the pressure in the intake manifold, which is measured by default.

In addition to the pressure, the temperature in the intake manifold is also measured by default. If the inlet valve of the combustion chamber is open, then the temperature Tc in the combustion chamber is at least approximately apparent from the temperature in the intake manifold and also the standard measured cooling water temperature TK of the internal combustion engine. Advantageously, when determining the mass flow ms, a temperature Tc in the combustion chamber is used, which is determined from the temperature TM in the intake manifold in conjunction with the cooling water temperature TK of the internal combustion engine.

The exhaust gas recirculation usually does not take place with a constant

Flow resistance, but is controlled by an exhaust gas recirculation valve, which can be either open or closed. The

Exhaust gas recirculation valve also has an open state

Flow resistance, so acts as a throttle. The most important variables from which the mass flow rriR of recirculated exhaust gas can at least approximately be determined are the pressure and the temperature of the exhaust gas before and after this throttle. The mass flow rriR of exhaust gas is thus advantageously controlled via an exhaust gas recirculation valve, and the pressure pv and the temperature Tv of the exhaust gas in the flow direction upstream of the exhaust gas recirculation valve are used to determine the mass flow rriR.

The pressure pv and the temperature Tv of the exhaust gas can be measured, for example. Corresponding sensors may be present, for example, in the context of exhaust gas aftertreatment. Also for the purpose of

Exhaust aftertreatment are characteristic of many internal combustion engines or computational models that indicate the pressure pv and the temperature Tv of the exhaust gas as a function of the operating point of the internal combustion engine. Thus, advantageously, the pressure pv and the temperature Tv of the exhaust gas are retrieved from a map or calculation model based on the operating point of the internal combustion engine.

The determination of the mass flow rriR to exhaust gas can advantageously be significantly refined by adopting the exhaust gas recirculation valve for determining the mass flow rriR as a throttle. Since pressure and temperature of the recirculated exhaust gas in the flow direction behind the exhaust gas recirculation valve in the intake manifold are measured by default and at the same time pressure pv and temperature Tv of the exhaust gas in the flow direction before the exhaust gas recirculation valve are known, with additional knowledge of the opening cross-section and the

Calculate the discharge rate of the exhaust gas recirculation valve rriR directly. The opening cross-section and the Ausflusszahl the exhaust gas recirculation valve are known as a function of the valve opening or can be determined for example on the test bench.

For example, the following throttle equation can be used to calculate rriR:

Here, A is the opening area and μ is the discharge rate of the

Exhaust gas recirculation valve, P _M is the standard measured pressure in the intake manifold, and pv is the density of recirculated exhaust gas upstream of the exhaust gas recirculation valve. Under the approximation that the exhaust gas is an ideal gas, pressure pv and temperature Tv in the flow direction in front of the exhaust gas recirculation valve depend on the gas equation

Pv - ^v v = ^R v - ^T v

together. Here vv is the specific volume and Rv is the specific gas constant of the recirculated exhaust gas. With vv = l / pv we get:

"_ Pv In order to make it plausible, in the above-derived formula for the mass flow ms through the intake manifold with the inlet valve open, the pressure pc can be replaced by the intake manifold pressure and the gas constant Rc can be replaced by the gas constant Rv of the mixture of air and recirculated exhaust gas Difference between ms and rriR match. If ΓΤΙΑ deviates in amount from this by more than a predetermined limit value, it is possible to deduce an error of the mass flow mA measured with the air mass meter. With a pressure-based mass air flow sensor, which measures the static pressure, the differential pressure and the temperature caused by the mass flow with separate sensors, this means that at least one of these sensors is defective. One possible reason for this is a change in the sensor characteristic as a result of environmental influences or aging.

After the above, the invention also relates to a

Air supply system for an internal combustion engine. The air supply system comprises a turbocharger, an air mass meter arranged behind the turbocharger in the flow direction, one downstream of the turbocharger

Air mass meter arranged throttle and arranged in the flow direction behind the throttle, a combustion chamber of the

Internal combustion engine upstream intake manifold. In addition, one opens

Exhaust gas recirculation line for exhaust gas of the internal combustion engine in the intake manifold.

According to the invention, the air mass meter is pressure-based

Air mass meter, and it is the only sensor for measuring the boost pressure and the charge air temperature provided.

It has been found that the method according to the invention makes it possible, in this configuration, to measure that measured by the air mass meter

Plausibilisieren mass flow mA of combustion air, without requiring the boost pressure sensor would be required as another redundant sensor. Thus, the boost pressure sensor can be saved. This saving, in turn, means that the use of the higher-quality pressure-based air mass meter ultimately causes no additional costs in the production. In a further advantageous embodiment of the invention, a sensor for direct measurement of the guided through the exhaust gas recirculation line mass flow rriR is connected to exhaust gas in the exhaust gas recirculation line. This can be one

comparatively inexpensive sensor, since only one sufficient for plausibility accuracy is needed.

After the above, there are embodiments of the method according to the invention, which work alone with data that can be measured with already existing sensors or can be retrieved from maps. In particular, such embodiments may therefore be fully implemented in software running on a controller. Other embodiments may be implemented at least partially in software on the controller. Such software can be sold, for example, as an update to existing control units and is therefore an independent product. Therefore, the invention also relates to a

A computer program product having machine-readable instructions which, when executed on a computer and / or on a controller, cause the computer and / or the controller to perform a method according to the invention.

Further measures improving the invention will be described in more detail below together with the description of the preferred embodiments of the invention with reference to figures.

embodiments

It shows:

Figure 1 embodiment of the air supply system and the method in a schematic representation;

Figure 2 shows an example of an exhaust gas recirculation valve 25, which is used in the air supply system or method. According to FIG. 1, combustion air 11 is drawn in through an exhaust-gas turbocharger 26, which is driven by exhaust gas 12 of internal combustion engine 1. The mass flow ΓΤΙΑ of the combustion air 11 is measured by a pressure-based air mass meter 13.

The combustion air 11 is fed through a throttle valve 14 to a suction pipe 15 and passes from there through an inlet valve 21 into the combustion chamber 20 of the cylinder 16 of the internal combustion engine 1 shown by way of example in FIG. 1. The combustion of, for example, petrol or gaseous fuel, whose supply is shown in FIG is not shown for clarity, drives a piston 17, which is coupled via a connecting rod 18 to a not shown in Figure 1 crankshaft. The exhaust gas 12 is through a

Exhaust valve 22 discharged from the combustion chamber 20. The cylinder 16 is surrounded by a cooling water jacket 19, the temperature Τκ is measured.

A portion of the exhaust gas 12 is returned through the exhaust gas recirculation line 28 in the intake manifold 15. In the exhaust gas recirculation line 28, a temperature sensor 23 is connected, which measures the temperature Tv of the exhaust gas 12 in the flow direction in front of the exhaust gas recirculation valve 25. In the exhaust gas recirculation line 28, a pressure sensor 24 is further connected, the pressure pv of the exhaust gas 12 in

Flow direction before the exhaust gas recirculation valve 25 measures. The temperature Tv and the pressure pv can optionally also be determined from the operating point of the

Internal combustion engine 1 can be retrieved from a map 27.

The plausibility of the mass flow [TIA measured by the air mass meter is now carried out in several steps. First, in step 110, the intake pipe temperature TM measured with the intake pipe temperature sensor 15b, the temperature Τκ of the cooling water jacket 19, and optionally further

Operating variables of the internal combustion engine 1, the temperature Tc derived in the combustion chamber 20. In the next step 120, the total mass flow ms flowing through the intake manifold 15 is determined from this temperature Tc in conjunction with the pressure PM in the intake manifold measured by the intake manifold pressure sensor 15a and the rotational speed n of the internal combustion engine 1. Therefore, in step 130, from temperature T and pressure pv of the recirculated exhaust gas 12 upstream of the exhaust gas recirculation valve 25, in conjunction with the intake pipe pressure PM, the mass flow rriR the recirculated exhaust gas 12 is determined. Optionally, this mass flow rriR can also be determined directly by a sensor 29 in the exhaust gas recirculation line 28.

From the total mass flow ms in the intake manifold 15 and the mass flow rriR to recirculated exhaust gas 12, a comparison value ΓΤΙΑ * for the mass flow ΓΤΙΑ of combustion air 11 is finally determined in step 140 by subtraction. If the air mass meter 13 functions correctly, ΓΤΙΑ * should be identical to rriA, except for any inaccuracies due to approximation. Is the

absolute deviation between ΓΤΙΑ * and ΓΤΙΑ greater than a predetermined limit, is on a fault condition of the air mass meter 13th

closed.

FIG. 2 schematically shows an exhaust gas recirculation valve 25 which can be used in the air supply system shown in FIG. The valve 25 consists of a valve body 25a, which is traversed by a channel 25b. The channel 25b is the input side connected to the exhaust gas recirculation line 28 and the output side to the intake manifold 15.

The channel 25b is closed by a valve plate 25d, which cooperates with a valve seat 25c. The valve disk can be moved via a valve rod 25e, which is displaceable with a servomotor 25f. In the open state of the valve 25, the exhaust gas 12 can pass through an opening area A, which is determined by the position of the valve disk 25 d. This position is measured via a stroke measurement 25g on the valve rod 25e. The valve 25 is connected via an electronic connection 25h with the

Engine control unit connected.

Claims

claims

1. A method for operating an internal combustion engine (1), wherein the mass flow ΓΤΙΑ of the intake combustion air (11) by a

Air mass meter is measured, characterized in that a pressure-based air mass meter (13) is selected and that the value of ΓΤΙΑ against the by a between the air mass meter (13) and at least one combustion chamber (20) of the internal combustion engine (1) connected suction pipe (15) flowing Mass flow ms is plausibilized (140), wherein the mass flow ms is determined in an operating state in which a mass flow rriR is recirculated to the exhaust gas (12) in the intake manifold (15), and in addition, the mass flow rriR is determined (130).

2. The method according to claim 1, characterized in that the

Mass flow ms from the air mass in the combustion chamber (20) and the speed n of the internal combustion engine is determined (120).

3. The method according to any one of claims 1 to 2, characterized

characterized in that the determination (120) of the mass flow ms is based on a temperature Tc in the combustion chamber (20) which is determined by the

Temperature TM in the intake manifold in conjunction with the cooling water temperature Τκ of the internal combustion engine (1) is determined (110).

4. The method according to any one of claims 1 to 3, characterized

characterized in that the mass flow rriR to exhaust gas via a

Exhaust gas recirculation valve (25) is controlled, wherein the pressure pv and the temperature Tv of the exhaust gas (12) in the flow direction before the

Exhaust gas recirculation valve (25) for determining the mass flow rriR

be used (130).

5. The method according to claim 4, characterized in that the pressure Pv and the temperature T of the exhaust gas (12) based on the operating point of the internal combustion engine (1) from a map or calculation model (27) are retrieved.

6. The method according to any one of claims 4 to 5, characterized

characterized in that the exhaust gas recirculation valve (25) is assumed to be the throttle for the determination of the mass flow rriR.

7. An air supply system for an internal combustion engine (1), comprising a turbocharger (26), in the flow direction behind the turbocharger (26) arranged air mass meter (13), in the flow direction behind the air mass meter (13) arranged throttle valve (14) and a in

Flow direction behind the throttle valve (14) arranged, a

Combustion chamber (20) of the internal combustion engine (1) upstream suction pipe (15), wherein an exhaust gas recirculation line (28) for exhaust gas (12) of the internal combustion engine (1) opens into the suction pipe (15), characterized in that the

Air mass meter (13) is a pressure-based air mass meter (13) and is provided as the only sensor for measuring the boost pressure and the charge air temperature.

8. Air supply system according to claim 7, characterized in that a sensor (29) for direct measurement of the exhaust gas recirculation line (28) guided mass flow rriR is connected to the exhaust gas (12) in the exhaust gas recirculation line (28).

9. Computer program product containing machine-readable

Instructions that, when on a computer, and / or on a computer

Control unit, cause the computer, and / or the control unit, to carry out a method according to one of claims 1 to 6.