DE10358462B4 - Device and method for determining the degree of contamination of an air filter unit for a motor vehicle internal combustion engine - Google Patents

Abstract

A method of detecting a degree of fouling of an air filter unit (1) for purifying air sucked by an automotive internal combustion engine (2) detecting an atmospheric pressure and a filtered air pressure from the atmospheric pressure and the filtered air pressure Determines the pressure difference and in which in an evaluation unit (20) the degree of contamination on the basis of a comparison between the determined pressure difference and a pollution-specific reference pressure difference is determined, wherein in at least one idling phase of the internal combustion engine (2) the pressure of the filtered air after flowing through a compressor unit (7) and before an at least partial inflow into at least one combustion chamber of the internal combustion engine (2) as charge pressure with a boost pressure sensor (4) is detected, characterized in that when switching an operating current of the internal combustion engine (2) of an ambient pressure sensor (3 ) and the pollution level of the air filter unit (1) to a central control and control unit (16), in particular a vehicle computer, is transmitted, and there compared with a permissible contamination characteristic value and as soon as the degree of contamination exceeds the permissible contamination characteristic value, a signal is transmitted to an output unit (17).

Description

The invention relates to a device and a method for determining a degree of contamination of an air filter unit for purifying air, which is sucked by a motor vehicle internal combustion engine, in which detects an atmospheric pressure and a pressure of the filtered air, from the atmospheric pressure and the pressure of the filtered air Determined pressure difference and in which the degree of contamination in an evaluation unit is determined on the basis of a comparison between the determined pressure difference and a pollution-specific reference pressure difference.

State of the art:

The ambient air contains a large number of impurities that can in some cases cause considerable damage to an internal combustion engine. For this reason, for example, motor vehicles have air filters that clean the air required for combustion in the engine. At the air filter here are two main requirements. Firstly, the intake air to be cleaned without the air passage is substantially impeded. On the other hand, the air filter should be designed so that the sometimes very strong intake noise of the air are effectively damped.

Depending on the landscape, soil and road conditions or intended use of a vehicle, the amount of dust contained in the ambient air varies between 0.001 and 1 g / m ³ [Bohner, M. et al. ; Expertise Automotive Technology; 25th edition; 1994; Publisher Europa-Lehrmittel; P. 250]. Dust, which enters the engine via the intake air, forms with the lubricating oil of the engine a grinding mass, which can lead to considerable wear, especially on cylinder liners, pistons and valve guides. Careful cleaning of the intake air therefore significantly determines the life of an engine.

In the known filter systems, the dust entrained by the sucked air is filtered out of the air by means of narrow sieves, narrow-pore filter materials, oil-wetted surfaces or by utilizing the centrifugal force in the filter. In this case, the filter material contained in each filter sometimes contaminates considerably. If a filter is not renewed or cleaned in time, the flow resistance of the filter increases and less air than required in the engine, so that ultimately a richer fuel-air mixture, a poorer filling and a lower engine performance may be the result of a filter contamination ,

For this reason, systems are known with which the degree of contamination of an air filter can be determined. The DE 197 10 981 A1 describes, for example, a method for determining the degree of contamination of a provided in the intake of an internal combustion engine, in particular a motor vehicle air filter. The pressure difference between the inlet and the outlet and thus the flow resistance of the air filter, which is a measure of the degree of contamination of the filter is determined from the atmospheric pressure before the air filter and the pressure prevailing in the intake manifold directly behind the air filter pressure. In the apparatus described in this document thus the degree of contamination of an air filter by means of a not arranged in the region of the intake manifold ambient pressure sensor, which is needed for the operation of an air conditioner or for the height correction of the injection quantity on the engine, and with a pressure sensor for regulating the injection quantity is provided in dependence on the boost pressure in the intake manifold, determined.

From the DE 197 30 578 A1 a method and a device for protecting a turbocharger is known. In order to minimize the number of sensors for operating characteristics, a map is provided, from which the intake air pressure of the supercharger is derived depending on the boost pressure, the engine speed and of the accelerator pedal position corresponding fuel quantity specification. Furthermore, means are provided which determine a limiting value for the amount of fuel metered to the internal combustion engine as a function of the intake air pressure.

Based on the known prior art, the invention is based on the object to provide a method and an apparatus for determining the degree of contamination of an air filter, in which no mounting space for a sensor must be provided in the region of the suction pipe directly behind the filter. The desired solution should moreover be cost-effective and, in particular, also be usable in internal combustion engines with turbocharging.

The object underlying the invention is achieved by a method according to claim 1 and a device according to claim 4, respectively. Advantageous developments of the inventive concept are the subject of the dependent claims and the following description text with reference to the embodiment refer.

According to the invention, a method for determining a degree of contamination of an air filter unit for purifying air, which is sucked by a motor vehicle internal combustion engine, in which an atmospheric pressure and a pressure of the detected filtered air, determined from the atmospheric pressure and the pressure of the filtered air, a pressure difference and in which in an evaluation unit, the degree of contamination is determined on the basis of a comparison between the determined pressure difference and a pollution-specific reference pressure difference, further developed such that in at least one idle phase of the internal combustion engine Pressure of the filtered air is detected after flowing through a compressor unit and before an at least partial inflow into at least one combustion chamber of the internal combustion engine as boost pressure with a boost pressure sensor.

The system according to the invention is thus distinguished by the fact that the monitoring of the degree of contamination of an air filter takes place with the aid of an ambient pressure and a charge pressure sensor. Both sensors are already present in particular in conventional diesel engines, such as those used in the commercial vehicle sector. Thus, the ambient pressure sensor realizes the height adjustment for the engine, while the boost pressure sensor is required for the regulation of the pressure of the intake air of the internal combustion engine. In this way, a reliable monitoring of the degree of contamination of an air filter can be ensured even with turbocharged diesel engines, without the need for additional sensors or additional mounting space in the region of the intake manifold behind the air filter.

The pollution-specific reference pressure values are preferably determined in advance of a standard use of the air filter on a test stand and / or during test drives. In such experiments, the flow resistance is determined for various levels of contamination of an air filter, which has the filter at the corresponding pollution.

The ambient pressure and boost pressure are measured while the engine is running. However, for the determination of the prevailing between the inlet and the outlet of the air filter differential pressure only values of the ambient pressure or the charge pressure are considered, which have been recorded during an idling phase of the internal combustion engine. At idle, the filtered air flows through the compressor unit without being compressed, so that the boost pressure sensor in this state of operation measures the intake vacuum relative to the ambient pressure.

Furthermore, according to the method according to the invention, the measured values detected by the ambient and boost pressure sensor are adjusted as soon as the operating current required for the operation of the internal combustion engine is switched on. As a rule, this switching on of the operating current is done by turning the ignition key. Preferably, in this case both measured values are set to zero, so that during the operation of the internal combustion engine, a subtraction of the detected pressures is relatively easy to make and measurement errors are excluded from zero-point drift.

Furthermore, the degree of contamination of the air filter to a central control and control unit, in particular a vehicle computer, transmitted. For this reason, the measured values acquired by the ambient pressure sensor or the boost pressure sensor are first converted into electrical signals which are made available to further data processing via a data line, for example a CAN bus or a VAN bus. Preferably, the pressure sensors have data interfaces, are fed via the corresponding measurement signals in the data line and so networking of the pressure sensors with at least one control unit is possible. It is irrelevant how the control unit, in particular a vehicle computer, is arranged relative to the pressure sensors.

Furthermore, the method according to the invention provides that the differential pressure values corresponding to specific degrees of contamination are likewise stored in the central control and control unit. Preferably, at the same time, a contamination characteristic value is also stored, which represents a limit value for just just permissible contamination of an air filter. In this connection, it is advantageous if the degree of contamination transmitted to the central control and control unit is compared with the permissible contamination characteristic value and, as soon as the degree of contamination exceeds the permissible contamination characteristic value, a corresponding signal, for example an electrical warning signal, is generated and transmitted to an output unit. Since the pollution usually increases continuously, predictions for the changeover date are possible on the one hand and on the other plausibility checks in the case of measured value jumps.

Preferably, the output unit generates an audible, visual and / or haptic warning signal which, for example, is perceptible by a vehicle driver while driving. Equally, however, it is also conceivable that at the same time or as an alternative a corresponding warning is stored in a data memory which is read out during an inspection of the internal combustion engine and / or of a vehicle with the aid of an external diagnostic system, for example in a workshop.

In any case, it makes sense that the warning signal is generated before the final capacity of the filter is reached to absorb soiling. Rather, the warning signal should become a Time are generated at the still a sufficiently long service life of the vehicle is guaranteed, without causing damage to the engine. In this preferred manner, a consumption or pollution-independent changing the air filter or the air filter cartridge is possible.

Furthermore, the object underlying the invention with a device for determining a degree of contamination of an air filter unit according to the preamble of claim 4 is achieved, which is characterized in that the pressure sensor as a boost pressure sensor with which the boost pressure, the filtered air after flowing through a compressor unit and before at least partially flowing into at least one combustion chamber of the internal combustion engine, is executed.

According to the device according to the invention, an input unit is provided, via which at least one permissible contamination characteristic value can be entered into the evaluation unit.

Furthermore, the evaluation unit preferably has at least one data interface via which the degree of contamination and / or when an admissible contamination characteristic value is exceeded, a warning signal can be transmitted to a central control and control unit, in particular a vehicle computer, and / or to an external data processing unit.

A particularly suitable embodiment also provides that the evaluation unit is integrated in a central control and control unit, in particular a vehicle computer.

In the following the invention with reference to an embodiment without limiting the general inventive concept will be described with reference to the figure.

Figure flow diagram of the intake air and the exhaust gases of an internal combustion engine

The figure shows schematically the use of a device for determining the degree of contamination of an air filter unit 1 for an internal combustion engine 2 a commercial vehicle, which consists of an ambient pressure sensor 3 and a boost pressure sensor 4 is formed. Both with the ambient pressure sensor 3 as well as the boost pressure sensor 4 These are sensors that are needed at the same time to implement additional functions in the vehicle.

The ones for combustion in the engine 2 required air is through a suction 5 sucked from the environment. The air here has the ambient pressure p _amb . The sucked fresh air first flows through an air filter 1 in which it is cleaned, in the suction line 18 , Subsequently, the cleaned fresh air through the designed as a so-called exhaust gas turbocharger compressor unit 7 via pressure line 6 , Exhaust gas recirculation control valve 8th and air distributor 9 the internal combustion engine 2 fed. The exhaust gas recirculation control valve (throttle valve) 8th is additionally via an exhaust gas recirculation line 21 with the manifold 10 connected.

The exhaust gas flow of the internal combustion engine 2 is via the manifold 10 to the turbine 11 the compressor unit 7 and to the muffler 12 the exhaust system 13 directed. To the compression in the compressor unit to the requirements of the engine 2 adjust, the boost pressure, with which the air is the engine 2 is supplied, regulated. About that in the exhaust system 13 provided, designed as a bypass valve boost pressure valve 14 the boost pressure is regulated by a data line 15 the measured values to the vehicle computer 16 be transferred and depending on the supercharging pressure, the boost pressure valve 14 is opened. When opening the charge pressure valve 14 Part of the exhaust gas flow bypasses the turbine 11 directly to the muffler 12 ,

In order to detect the respective charge pressure is in the flow direction of the air behind the compressor unit 7 a boost pressure sensor 4 provided that detects a measured value for the boost pressure and to a vehicle computer 16 forwards. For engine control takes place in the vehicle computer 16 finally, a data processing of the boost pressure values. Depending on the operating state of the internal combustion engine is also the pressure relief valve 19 controlled in order to be able to regulate the amount of air to be compressed in this way.

In addition, the ambient pressure sensor detects 3 during operation of the internal combustion engine 2 the ambient pressure p _amb to in the vehicle _computer 16 to make a height adjustment for the engine control.

To with the help of the ambient pressure sensor 3 and the boost pressure sensor 4 the degree of contamination of the air filter 1 will be able to capture when starting the engine 2 from the ambient 3 as well as the boost pressure sensor 4 recorded measured values to a in the vehicle computer 16 integrated evaluation unit 20 transmitted and adjusted by first setting both measured values to zero. As soon as the engine 2 is in an idling phase, the engine 2 So is not charged with a load, the intake air of the engine 2 in the compressor unit 7 not compacted. A pressure difference arising in this operating condition of the engine 2 is set between the ambient pressure and the boost pressure is therefore solely on flow resistance of the intake before the boost pressure sensor 4 due. Since the pipe friction losses in the intake pipe compared to the flow resistance of the air filter 1 are negligible, the measured pressure difference between the ambient pressure and the boost pressure corresponds to the flow resistance of the air filter 1 ,

For determining the degree of soiling of the air filter 1 , In the idling phase of the internal combustion engine, the ambient pressure sensor 3 as well as boost pressure sensor 4 detected pressure difference between ambient and boost pressure measured and the measured value to the in the vehicle computer 16 integrated evaluation unit 20 forwarded. In the evaluation unit 20 or in the vehicle computer 16 Reference data are stored, each on the air filter 1 adjoining pressure difference to a degree of contamination. In this way with the evaluation unit 20 in the vehicle computer 16 determined pollution level is the driver in a vehicle display 17 displayed and / or read during the inspection of the vehicle in a workshop with an external data processing unit from the vehicle computer. Exceeds the degree of contamination of the air filter 1 between the inspections a permissible value, this is the driver in the vehicle display 17 displayed. The limit for the permissible degree of contamination of the air filter 1 In any case, it will be chosen so that even after the air filter is displayed 1 or the air filter cartridge must be changed, an operation of the engine 2 is possible for a certain amount of time without causing engine damage.

Of course, it is also conceivable in this context that an impermissible degree of contamination is automatically forwarded to a workshop during the operation of a vehicle so that corresponding replacement parts can be prepared in a timely manner.

The above-described detection of the degree of contamination of the air filter 1 based on the detection of the air filter 1 applied pressure difference with anyway required for the operation of the vehicle sensors. This highly relevant for the operation of an internal combustion engine measurement is very reliable and without that in the range of the intake manifold in this way 18 that attach to the air filter 1 Connects a sensor element must be provided carried out.

LIST OF REFERENCE NUMBERS

1

air filter

2

internal combustion engine

3

Atmospheric pressure sensor

4

Boost pressure sensor

5

suction

6

pressure line

7

compressor unit

8th

Exhaust gas recirculation control valve (throttle)

9

air distributor

10

manifold

11

turbine

12

silencer

13

exhaust system

14

Boost Valve

15

data line

16

vehicle computer

17

vehicle display

18

suction tube

19

Pressure relief valve

20

evaluation

21

Exhaust gas recirculation line

Claims (6)

Method for determining a degree of soiling of an air filter unit ( 1 ) for the purification of air from an automotive internal combustion engine ( 2 ), in which an atmospheric pressure and a pressure of the filtered air is detected, a pressure difference is determined from the atmospheric pressure and the pressure of the filtered air and in which an evaluation unit (in 20 ) the degree of contamination is determined on the basis of a comparison between the determined pressure difference and a pollution-specific reference pressure difference, wherein in at least one idling phase of the internal combustion engine ( 2 ) the pressure of the filtered air after flowing through a compressor unit ( 7 ) and before an at least partial inflow into at least one combustion chamber of the internal combustion engine ( 2 ) as boost pressure with a boost pressure sensor ( 4 ) is detected, characterized in that when switching an operating current of the internal combustion engine ( 2 ) of an ambient pressure sensor ( 3 ) and ambient pressure from the boost pressure sensor ( 4 ) and that the degree of contamination of the air filter unit ( 1 ) to a central control and control unit ( 16 ), in particular a vehicle computer, and there compared with a permissible contamination characteristic value and as soon as the degree of contamination exceeds the permissible contamination characteristic value a signal to an output unit ( 17 ) is transmitted. Method according to claim 1, characterized in that the output unit ( 17 ) generates an acoustic, visual and / or haptic warning signal. Method according to claim 1 or 2, characterized in that the degree of soiling and / or or the exceeding of the contamination index is transmitted to an external data processing unit. Device for determining a degree of contamination of an air filter unit ( 1 ) for the purification of air from an automotive internal combustion engine ( 2 ) is sucked in, with a sensor unit, which via an ambient pressure sensor ( 3 ), with which an atmospheric pressure can be detected and via a pressure sensor ( 4 ), with which the pressure of the filtered air behind the air filter unit ( 1 ) and has an evaluation unit ( 20 ), in which from the atmospheric pressure and the pressure of the filtered air, a pressure difference can be determined and on the basis of a comparison between the pressure difference and a pollution-specific reference pressure difference, the degree of contamination can be determined, wherein the pressure sensor ( 4 ) as a boost pressure sensor, with which the boost pressure, the filtered air after flowing through a compressor unit ( 7 ) and at least partially inflow into at least one combustion chamber of the internal combustion engine ( 2 ), is executed, characterized in that an input unit is provided, via which at least one permissible contamination characteristic value in the evaluation unit ( 20 ) and that the evaluation unit ( 20 ) has at least one data interface, and that at least one output unit ( 17 ) is provided with the basis of the pollution index and the degree of contamination, a signal is generated as soon as the degree of pollution assumes a higher value than the pollution index. Apparatus according to claim 4, characterized in that the evaluation unit ( 20 ) has at least one data interface via which the degree of contamination and / or the signal to a central control and control unit ( 16 ), in particular a vehicle computer, and / or can be transmitted to an external data processing unit. Device according to one of claims 4 or 5, characterized in that the evaluation unit ( 20 ) into a central control and control unit ( 16 ), in particular a vehicle computer, is integrated.

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