阅读说明：本技术 空气质量测量装置的可信度检验 (Plausibility check of an air quality measuring device ) 是由 M·申克 P·博伊尔勒 于 2018-05-28 设计创作，主要内容包括：一种用于运行内燃机(1)的方法,其中,通过空气质量测量装置测量吸入的燃烧用空气(11)的质量流m<Sub>A</Sub>,其中,选择基于压力的空气质量测量装置(13),其中,相对于流过连接在所述空气质量测量装置(13)与所述内燃机(1)的至少一个燃烧室(20)之间的进气管(15)的质量流m<Sub>s</Sub>来对m<Sub>A</Sub>的值进行可信度检验(140),其中,在如下运行状态中求取质量流m<Sub>s</Sub>：在所述运行状态中,废气(12)的质量流m<Sub>R</Sub>再循环到所述进气管(15)中,其中,附加地求取(130)质量流m<Sub>R</Sub>。一种用于内燃机(1)的空气供应系统,所述空气供应系统包括：涡轮增压器(26)、在流动方向上布置在所述涡轮增压器(26)之后的空气质量测量装置(13)、在流动方向上布置在所述空气质量测量装置(13)之后的节流活门(14)、在流动方向上布置在所述节流活门(14)之后并且连接在所述内燃机(1)的燃烧室(20)之前的进气管(15),其中,用于内燃机(1)的废气(12)的废气再循环管线(28)通入到所述进气管(15)中,其中,空气质量测量装置(13)是基于压力的空气质量测量装置(13),并且空气质量测量装置设置成用于测量增压压力和增压空气温度的唯一传感器。一种所属的计算机程序产品。(A method for operating an internal combustion engine (1), wherein a mass flow m of intake combustion air (11) is measured by an air mass measuring device A Wherein a pressure-based air mass measuring device (13) is selected, wherein the mass flow m relative to the mass flow through an intake pipe (15) connected between the air mass measuring device (13) and at least one combustion chamber (20) of the internal combustion engine (1) is selected s To m A Is subjected to a plausibility check (140), whereinIn the following operating states, the mass flow m is determined s : in the operating state, the mass flow m of the exhaust gas (12) R Is recirculated into the intake pipe (15), wherein additionally a mass flow m is determined (130) R . An air supply system for an internal combustion engine (1), the air supply system comprising: a turbocharger (26), an air mass measuring device (13) arranged downstream of the turbocharger (26) in the flow direction, a throttle flap (14) arranged downstream of the air mass measuring device (13) in the flow direction, an intake pipe (15) arranged downstream of the throttle flap (14) in the flow direction and connected upstream of a combustion chamber (20) of the internal combustion engine (1), wherein an exhaust gas recirculation line (28) for exhaust gases (12) of the internal combustion engine (1) opens into the intake pipe (15), wherein the air mass measuring device (13) is a pressure-based air mass measuring device (13) and is provided as the only sensor for measuring the charge pressure and the charge air temperature. An associated computer program product.)

1. Method for operating an internal combustion engine (1), wherein an air mass is passedThe measuring device measures the mass flow m of the sucked-in combustion air (11)_ACharacterized in that a pressure-based air mass measuring device (13) is selected and is oriented relative to a mass flow m through the intake pipe (15)_STo m_AIs checked (140) for plausibility, the intake pipe being connected between the air mass measuring device (13) and at least one combustion chamber (20) of the internal combustion engine (1), wherein, in an operating state, a mass flow m is determined_SWherein, in the operating state, the mass flow m of the exhaust gas (12)_RIs recirculated into the intake pipe (15), wherein the mass flow m is additionally determined (130)_R。

2. Method according to claim 1, characterized in that the mass flow m is determined (120) from the air mass in the combustion chamber (20) and the rotational speed n of the internal combustion engine_S。

3. Method according to claim 1 or 2, characterized in that it is based on the temperature T in the combustion chamber (20)_CTo find (120) said mass flow m_SFrom the temperature T in the inlet line_MIn combination with the temperature T of the cooling water of the internal combustion engine (1)_KTo determine (110) the temperature T in the combustion chamber_C。

4. A method according to any one of claims 1-3, characterized by controlling the mass flow m of exhaust gases by means of an exhaust gas recirculation valve (25)_RWherein the pressure p of the exhaust gas (12) upstream of the exhaust gas recirculation valve (25) in the flow direction is taken into account_vAnd temperature T_vTo find (130) said mass flow m_R。

5. Method according to claim 4, characterized in that the pressure p of the exhaust gas (12) is recalled from a characteristic map or a calculation model (27) as a function of the operating point of the internal combustion engine (1)_vAnd temperature T_v。

6. According to the rightThe method of claim 4 or 5, characterized in that m is the mass flow_RIs determined, the exhaust gas recirculation valve (25) is designated as a throttle.

7. An air supply system for an internal combustion engine (1), the air supply system comprising: a turbocharger (26), an air quality measuring device (13), a throttle valve (14) and an air inlet pipe (15), the air mass measuring device is arranged downstream of the turbocharger (26) in the flow direction, the throttle flap is arranged downstream of the air quality measuring device (13) in the flow direction, the intake pipe is arranged downstream of the throttle flap (14) in the flow direction and upstream of a combustion chamber (20) of the internal combustion engine (1), wherein an exhaust gas recirculation line (28) for the exhaust gases (12) of the internal combustion engine (1) opens into the intake pipe (15), characterized in that the air quality measuring device (13) is a pressure-based air quality measuring device (13), and the air mass measuring device is provided as the only sensor for measuring the charge pressure and the charge air temperature.

8. Air supply system according to claim 7, characterised in that the following sensors (29) are connected into the exhaust gas recirculation line (28): for directly measuring the mass flow m of exhaust gas (12) conducted through the exhaust gas recirculation line (28)_R。

9. A computer program product comprising machine-readable instructions which, when implemented on a computer and/or on a control device, cause the computer and/or the control device to carry out the method according to any one of claims 1 to 6.

Technical Field

The invention relates to a method for operating an internal combustion engine, in which a malfunction of an air quality measuring device can be detected, and to an air supply system for an internal combustion engine, which is provided for this purpose.

Background

An air mass measuring device is used in the intake tract of an internal combustion engine in order to ensure an optimum degree of filling of the combustion chamber and thus an optimum combustion. The power output by the gasoline engine is proportional to the intake air mass flow. Correctly measuring the air mass flow is of important relevance for safety. Therefore, legal regulations require that the correct functioning of the air quality measuring device should be monitored.

It is known from US 5291803A, DE 19946874 Al and DE 102010044164 Al to check the plausibility of an air mass flow determined by an air mass measuring device by means of a comparison value which is obtained by a further sensor which is independent of the air mass measuring device. If the air mass flow deviates too far from the comparison value, this can be evaluated as a fault-present behavior.

Disclosure of Invention

Within the scope of the inventionA method for operating an internal combustion engine has been developed in the domain. The mass flow m of the sucked-in combustion air (Verbrennungslift) is measured by an air mass measuring device_A。

According to the invention, a pressure-based air quality measurement device is selected. Relative to mass flow m through the inlet pipe_STo m_AIs checked for plausibility, the intake pipe being connected between the air mass measuring device and at least one combustion chamber of the internal combustion engine. In this case, the mass flow m is determined in the operating state_SWherein the mass flow m of the exhaust gas is adjusted in the operating state_RIs recirculated into the intake pipe, wherein the mass flow m is additionally determined_R。

It has been recognized that the mass flow m is independent of the position of the throttle flap arranged between the air mass measuring device and the intake manifold_SShould nominally be equal to mass flow m_AWith mass flow m of recirculated exhaust gas_RAnd (4) summing. It has furthermore been recognized that the mass flow m through the inlet line_SAnd exhaust gas mass flow m_RCan be derived from variables which are provided by sensors which are present in the internal combustion engine under standard conditions (at least with sufficient accuracy for plausibility checks). Thus, redundant sensors can be omitted. This provision for monitoring the correct functioning of the air quality measuring device can therefore be met with low expenditure.

According to the prior art, the pressure and temperature of the air before the pressure is relieved via the throttle flap have been measured, for example, by means of a boost pressure sensor, and this relief pressure has been modeled by means of a throttle equation. By measuring the intake manifold pressure, the mass flow through the throttle flap can then be determined as m_AThe comparison value of (1). In contrast, the plausibility check according to the invention has the following advantages: a boost pressure sensor is not required and thus cost can be saved.

Particularly advantageous is the combination with a Pressure-based air quality measuring device, for example of the PFM (Pressure-based Flow Meter) type. Such air mass measuring devices measure the static pressure as a reference pressure and the pressure difference caused by the mass flow, as well as the temperature of the air. This therefore involves a relatively expensive sensor, which can simultaneously assume the function of a charge pressure sensor for this purpose, since the static pressure corresponds to the charge pressure and the temperature corresponds to the charge air temperature. It is obvious that an additional boost pressure sensor can be used for plausibility checking of the air quality measuring device. However, if used solely as such a control mechanism, the boost pressure sensor is too expensive.

Instead of determining the recirculated exhaust gas mass flow m_RIn principle, the exhaust gas mass flow can be set to zero by temporarily disabling exhaust gas recirculation. However, this has a significant disadvantage, even in active exhaust gas recirculation, in comparison with the plausibility check implemented according to the invention. In particular in natural gas engines for commercial vehicles, it is not possible to shut off the exhaust gas recirculation at every operating point of the engine, since the exhaust gas recirculation is used there primarily to reduce the combustion chamber temperature or the engine outlet temperature and is necessary to protect the turbocharger and other components. Operating states in which exhaust gas recirculation is temporarily not required occur very rarely during driving operation. In order to carry out a defined plausibility check of the air quality measuring device, it may therefore be necessary to briefly force the following operating states: in this operating state, exhaust gas recirculation is temporarily disabled. This may mean, for example: the engine torque must be reduced in order to avoid overheating of the internal combustion engine or the exhaust train. On the one hand, this may be unpleasant for the driver, since sometimes the full requested engine torque is not available. On the other hand, when exhaust gas recirculation is disabled, it is necessary to adjust the ignition angle in a later direction as necessary, which reduces combustion efficiency and increases fuel consumption.

In a particularly advantageous embodiment of the invention, the mass flow m is determined from the air mass in the combustion chamber and the rotational speed n of the internal combustion engine_S. Mass flow m_SFor example, the following formula can be used:

here, the fraction represents the mass of air in the combustion chamber in the following approximation: air is considered an ideal gas. p is a radical of_c、V_cAnd T_cRespectively the pressure, volume and temperature of the air in the combustion chamber, R_cIs a specific gas constant of the air in the combustion chamber, n is the engine speed, and f (n) is a multiplication factor dependent on the engine speed.

Determining p at the moment when the inlet valve of the combustion chamber is opened_c、V_cAnd T_cIs particularly easy. Then, V_cCorresponding to the effective working volume, p, of the internal combustion engine_cApproximately corresponding to the pressure in the inlet line measured in the normal case.

In the standard case, the temperature is measured in addition to the pressure in the intake manifold. Temperature T in the combustion chamber if the intake valve of the combustion chamber is open_cAt least approximately from the temperature in the intake manifold and the temperature T of the cooling water of the internal combustion engine, which is likewise measured under standard conditions_KAnd (6) obtaining. Advantageously, therefore based on the temperature T in the combustion chamber_cDetermining mass flow m_SFrom the temperature T in the inlet pipe_MCombined with temperature T of cooling water of internal combustion engine_KTo find the temperature in the combustion chamber.

Exhaust gas recirculation is not usually performed with a constant flow resistance, but rather is controlled by an exhaust gas recirculation valve, which can be either open or closed. The exhaust gas recirculation valve also has a flow resistance in the open state, so that the exhaust gas recirculation valve acts as a throttle. The mass flow m of the recirculated exhaust gas can be determined at least approximately_RThe most important parameters of (2) are: pressure and temperature of the exhaust gas before and after the restriction. It is therefore advantageous to control the mass flow m of the exhaust gas by means of an exhaust gas recirculation valve_RAnd the use of the pressure pv and the temperature T of the exhaust gas upstream of the exhaust gas recirculation valve in the flow direction is taken into account_vTo find the mass flow m_R。

For example, the pressure pv and the temperature T of the exhaust gas can be measured_v. Corresponding transmissionThe sensor may be present, for example, in the context of exhaust gas aftertreatment. For the purpose of exhaust gas aftertreatment, however, there are also a number of characteristic maps or calculation models of internal combustion engines which specify the pressure pv and the temperature T of the exhaust gas_vAs a function of the operating point of the internal combustion engine. Advantageously, therefore, the pressure pv and the temperature T of the exhaust gas are retrieved from a characteristic map or a calculation model as a function of the operating point of the internal combustion engine_v。

Advantageously, by applying a current m to said mass flow_RThe determination of (a) by identifying the exhaust gas recirculation valve as a throttle, the mass flow m of the exhaust gas can be significantly reduced_RObtaining the target value. Since the pressure and temperature of the recirculated exhaust gas in the intake pipe downstream of the exhaust gas recirculation valve in the flow direction are measured in the standard case and the pressure pv and temperature T of the exhaust gas upstream of the exhaust gas recirculation valve in the flow direction are known at the same time_vTherefore, when additionally knowing the opening cross section and the emission coefficient (ausflussizahl) of the exhaust gas recirculation valve, m can be calculated directly_R. The opening cross section and the emission coefficient of the exhaust gas recirculation valve are known as a function of the valve opening or can be determined, for example, on a test bench.

For example, m can be calculated using the following throttling equation_R：

Wherein

Here, a is an opening cross section of the exhaust gas recirculation valve, and μ is a discharge coefficient of the exhaust gas recirculation valve. p is a radical of_MIs the pressure, p, measured in the intake pipe under standard conditions_vIs the density of the recirculated exhaust gas in the flow direction before the exhaust gas recirculation valve. In the approximate case of an exhaust gas which is an ideal gas, the pressure p upstream of the exhaust gas recirculation valve in the flow direction_vAnd temperature T_vAre related by:

p_V·v_V＝R_V·T_V

here, v_vIs the specific volume of the recirculated exhaust gas, and R_vIs the specific gas constant of the recirculated exhaust gas. By means of v_v＝1/ρ_vObtaining:

now, in order to pair m_AA plausibility check is carried out, the mass flow m through the intake pipe being derived above with regard to the opening of the intake valve_sCan be replaced by the intake pipe pressure and the gas constant R can be replaced by the gas constant Rv (of the mixture of air and recirculated exhaust gas)_c. Then, m_AShould correspond to m_sAnd m_RThe difference between them. If m is_AIf the deviation from this value exceeds a predetermined limit value in magnitude, it can be concluded that the mass flow m measured by the air mass measuring device is present_AThere is an error. For pressure-based air quality measuring devices, which measure static pressure, pressure differences caused by mass flow and temperature by means of separate sensors, this likewise means that at least one of these sensors is defective. One possible reason for this is that the sensor characteristic changes due to environmental influences or aging.

As mentioned above, the invention also relates to an air supply system for an internal combustion engine. The air supply system includes: the device comprises a turbocharger, an air mass measuring device arranged downstream of the turbocharger in the flow direction, a throttle flap arranged downstream of the air mass measuring device in the flow direction, and an intake pipe arranged downstream of the throttle flap in the flow direction and connected upstream of the combustion chamber of the internal combustion engine. In addition, an exhaust gas recirculation line (for the exhaust gas of the internal combustion engine) opens into the intake manifold.

According to the invention, the air mass measuring device is a pressure-based air mass measuring device and is provided as the only sensor for measuring the charge pressure and the charge air temperature.

It has been realized that the method according to the invention can be implemented in said configuration: mass flow m of combustion air measured by air mass measuring device_AA plausibility check is carried out, for which purpose the boost pressure sensor is not required as a further redundant sensor. Therefore, the boost pressure sensor can be omitted. This omission in turn leads to: the use of higher quality pressure-based air quality measurement devices ultimately does not incur any additional expense in manufacturing.

In a further advantageous embodiment of the invention, the following sensors are connected in the exhaust gas recirculation line: the sensor is used for directly measuring the mass flow m of the exhaust gas guided through the exhaust gas recirculation line_R. This can be a relatively inexpensive sensor, since only sufficient accuracy for the plausibility check is required.

As mentioned above, there are the following embodiments of the method according to the invention: the embodiment processes the data separately, which can be measured by sensors present anyway or can be called from a family of characteristic curves. In particular, such an embodiment can therefore be implemented completely in software running on the control device. Other embodiments may be implemented at least in part in software on a control device. Such software can be sold, for example, as an update to an existing control device and is therefore a stand-alone product. The invention therefore also relates to a computer program product having machine-readable instructions which, when executed on a computer and/or control device, cause the computer and/or control device to carry out the method according to the invention.

Drawings

Further measures to improve the invention are shown in more detail below in connection with the description of preferred embodiments of the invention with reference to the figures.

The figures show:

fig. 1 shows an embodiment of the air supply system and of the method in a schematic view;

fig. 2 shows an exemplary illustration of an exhaust gas recirculation valve 25 which can be used in the air supply system or the method.

Detailed Description

According to fig. 1, combustion air 11 is drawn in by an exhaust gas turbocharger 26, which is driven by the exhaust gas 12 of the internal combustion engine 1. Mass flow m of combustion air 11 by means of a pressure-based air mass measuring device 13_AThe measurement is performed.

Combustion air 11 is supplied to an intake manifold 15 via a throttle flap 14, and from there it passes via an intake valve 21 into a combustion chamber 20 of a cylinder 16, which is shown by way of example in fig. 1, of the internal combustion engine 1. The combustion of the gasoline or gaseous fuel drives a piston 17 which is coupled by a connecting rod 1 to a crankshaft, not shown in fig. 1, the delivery of the gasoline or gaseous fuel not being shown in fig. 1 for the sake of clarity. The exhaust gas 12 is discharged from the combustion chamber 20 through a discharge valve 22. The cylinder 16 is surrounded by a cooling water jacket 19, and the temperature T of the cooling water jacket 19 is controlled_KThe measurement is performed.

A portion of the exhaust gas 12 is recirculated into the inlet pipe 15 through an exhaust gas recirculation line 28. Connected in the exhaust gas recirculation line 28 is a temperature sensor 23, which measures the temperature T of the exhaust gas 12 upstream of the exhaust gas recirculation valve 25 in the flow direction_v. A pressure sensor 24 is also connected in the exhaust gas recirculation line 28, which measures the pressure p of the exhaust gas 12 upstream of the exhaust gas recirculation valve 25 in the flow direction_vThe measurement is performed. The temperature T can optionally also be retrieved from the characteristic map 27 as a function of the operating point of the internal combustion engine 1_vAnd pressure p_v。

Mass flow m measured by an air mass measuring device_AThe plausibility check of (2) is now carried out in a plurality of steps. First, in step 110, the temperature T in the combustion chamber 20 is derived from_c: intake pipe temperature T measured by means of intake pipe temperature sensor 15b_MTemperature T of cooling water jacket 19_KAnd (optionally) other operating variables of the internal combustion engine 1. In a next step 120, the temperature T is measured_cCombined with the pressure p in the inlet line_MAnd rotation of the internal combustion engine 1Speed n to determine the total mass flow m through the inlet line 15_SThe pressure in the intake pipe is measured by an intake pipe pressure sensor 15 a.

In active exhaust gas recirculation, the mass flow m_SConsisting of a mixture of combustion air 11 and recirculated exhaust gas 12. Thus, in step 130, the mass flow of the recirculated exhaust gas 12 is found by: temperature T of recirculated exhaust gas 12 upstream of exhaust gas recirculation valve 25 in the flow direction_vAnd pressure p_vIntake pipe pressure p_M. Alternatively, the mass flow m can also be determined directly by a sensor 29 in the exhaust gas recirculation line 28_R。

Finally, in step 140, the total mass flow m in the inlet line 15 is measured_SAnd mass flow m of recirculated exhaust gas 12_RDifferencing to determine the mass flow m of the combustion air 11_AComparison value m of_A*. In the case where the air quality measuring device 13 is operating normally, m is not only inaccurate due to the approximation_AShould be related to m_AThe same is true. If m is_AAnd m_AIf the deviation between the values is greater in magnitude than a predetermined limit value, it is concluded that a fault state exists in the air quality measuring device 13.

Fig. 2 schematically shows an exhaust gas recirculation valve 25 which can be used in the air supply system shown in fig. 1. The valve 25 is constituted by a valve body 25a, which is crossed by a passage 25 b. The channel 25b is connected on the input side to the exhaust gas recirculation line 28 and on the output side to the intake pipe 15.

The passage 25b can be closed by a valve disk 25d interacting with a valve seat 25 c. The valve disc can be moved by a valve rod 25e which can be moved by means of a servomotor 25 f. In the open state of the valve 25, the exhaust gas 12 can pass through an opening area a determined by the position of the valve disc 25 d. This position is measured by a stroke measurement 25g on the valve stem 25 e. The valve 25 is connected to the engine control via an electronic connection 25 h.