EP3575581A1 - Method for controlling a control valve - Google Patents

Abstract

Method for controlling a control valve (1), the control valve (1) regulating a volume flow (2) of a fluid (3) along a line (16, 17); the method comprising at least the following steps: a) performing a closing process (8) of the control valve (1); b) measuring a pressure profile (9) upstream of the control valve (1); c) determining a density of the fluid (3).

Description

The invention relates to a method for controlling a control valve, in particular a control valve of a tank ventilation system, preferably the tank ventilation system of a motor vehicle.

Control valves in tank ventilation systems regulate a volume flow from a filter (an adsorbent) of a tank towards a suction pipe (or a connecting path between the filter and at least one combustion chamber) of an internal combustion engine.

The filter is regularly an activated carbon filter which binds the components of the fluid (eg a fuel) stored in the tank, which have been degassed from the tank. The activated carbon filter can be fluidly connected to the intake manifold of the internal combustion engine via the control valve, so that the fluid bound or temporarily stored in the filter can be supplied to the combustion chamber in a regulated manner.

For the calculation of the amount of fuel to be injected, it is necessary to know the amount of fuel supplied by the tank ventilation system.

The determination of the tank ventilation system supplied amount is currently z. B. allows via lambda probes. For this purpose, the control valve of the tank ventilation system is opened slowly and the deviation from a setpoint for lambda (fuel-air ratio, is determined by exhaust gas sensors) is monitored. It is assumed that this deviation results exclusively from the supply of fuel from the tank ventilation system. For this purpose, however, a signal downstream of the combustion chamber is evaluated, ie it must first occur a deviation from the desired value for lambda before a control can take place. This results in an increase in raw emissions. Further, all the mixture deviations are returned to the fuel supplied from the tank venting system. In the case of an inaccurate mixture pilot control (and a deviation from a target value for the mixture), the calculated fuel fraction does not correspond to the actual fuel fraction. As a result, the tank ventilation must be very carefully controlled or severely limited so as not to produce too great an impact on the smoothness and the raw emissions of the internal combustion engine.

From the WO 2012/049219 A1 It is known to use a pump for the promotion of scavenging air, so that the fuel can be sucked out of the filter targeted and fed to the internal combustion engine.

The object of the present invention is at least partially to solve the problems mentioned with reference to the prior art. In particular, a method for controlling a control valve is to be proposed by which a more accurate control of the combustion chamber supplied proportion of fuel is made possible.

To solve these problems, a method with the features according to claim 1 contributes. Advantageous developments are the subject of the dependent claims. The features listed individually in the claims can be combined in a technologically meaningful manner and can be supplemented by explanatory facts from the description and / or details of the figures, with further embodiments of the invention are shown.

1. a) Durchführen eines Schließvorganges des Regelventils; und
2. b) Messen eines Druckverlaufs stromaufwärts des Regelventils;
3. c) Bestimmen einer Dichte (Masse pro Volumen, also [Kilogramm/Kubikmeter]) des Fluids.

A method for controlling a control valve is proposed, wherein the control valve regulates a volume flow of a fluid along a line (first line, second line, ie through the line), in particular from a filter of a tank to a suction pipe of an internal combustion engine. The method has at least the following steps:

1. a) performing a closing operation of the control valve; and
2. b) measuring a pressure profile upstream of the control valve;
3. c) Determining a density (mass per volume, ie [kilogram / cubic meter]) of the fluid.

The control valve regulates in particular a volume flow along a connecting path between the filter and the internal combustion engine. Possibly. the connection path is connected to the intake manifold via a discharge point.

In particular, steps a) to c) are carried out in the order described. In particular, steps a) and b) are performed at least temporarily parallel to one another. The step c) takes place in particular taking into account the pressure curve, that is preferably temporally after step b).

In particular, at least one minimum and one maximum of the pressure profile are detected in step b). In particular, a minimum of the pressure curve is detected, which is present in the pressure curve immediately before the closing of the control valve. In particular, a maximum of the pressure curve is detected, which is present in the pressure curve immediately after the closing of the control valve.

Closing the control valve comprises, in particular, that in the closed state of the control valve, no volume flow can flow via the control valve.

The measuring of the pressure curve is effected in particular by a continuous or intermittent sensory detection of a pressure condition. Concrete sensor readings can be cumulated. Single values of the pressure measurement can be averaged and / or stored. The pressure profile can be characterized or analyzed using the following pressure parameters: maximum values, minimum values, deviations from measured or predefinable measurement or threshold values, rate of change.

The determination of the density of the fluid can be carried out on the basis of measured pressure states or pressure parameters derived therefrom, optionally with the inclusion of one of the abovementioned pressure parameters. The determination The density of the fluid can be determined in particular by evaluating (at least) the minimum and maximum of the pressure profile.

In particular, in a further step i), the volumetric flow of the fluid flowing via the at least partially opened control valve can be determined (for example, detected by measurement via a hot-film sensor or the like). In particular, the volume flow can be determined immediately before initiating the closing operation according to step a). In particular, the volume flow can be determined in the process of opening the control valve following the closing operation in accordance with step a). The volume flow is detected in particular by measurement.

With knowledge of density and volume flow, at least a first portion of a first component of the fluid and a second portion of a second component of the fluid can be determined.

In particular, the first component is air and the second component is a fuel. The fuel is at least partially, in particular completely gaseous. Possibly. the fuel may be present as a liquid.

In a further step ii), a temperature of the fluid can be determined. Knowing the temperature determines the density of the fluid (with a higher accuracy). In particular, the temperature is measured together with the pressure, z. B. by a combined sensor (pressure / temperature sensor).

The control valve is clocked in particular with at least one frequency or opens and closes in frequency. In particular, a pulsed volume flow of the fluid can thus be provided via the control valve.

The method, in particular at least steps a) to c), optionally additionally at least one of steps i) and ii) (or both) is carried out at least in two, three, four or more consecutive closing operations, in particular during each closing operation.

In particular, the density determined according to step c) can be verified by repeatedly performing the method. Possibly. it is possible to average the values determined for the density.

The frequency is in particular between 5 and 50 hertz, preferably between 5 and 20 hertz.

The control valve is controlled in particular by means of a (PWM) signal (pulse width modulation), whereby, in particular, a successive opening of the control valve occurs at a certain duty cycle. In particular, a volumetric flow flowing via the control valve can be controlled via the duty cycle.

In particular, a control of a fuel addition of the internal combustion engine is performed depending on the specific density of the fluid.

By determining the density of the fuel fraction can be determined in the fluid, so that a more precise addition of a predetermined amount of fuel is possible via the controlled opening of the control valve.

In particular, the pressure sensor is arranged between the filter and the control valve.

The control valve is in particular designed so that a pulsed volume flow is passed through the control valve to the suction line. In particular, the control valve is controlled via a PWM signal.

During the open phase of the control valve, a flow of the fluid is formed. If the control valve then closes, the volume flow of the fluid is interrupted abruptly. This leads to a measurable increase in pressure upstream of the control valve. The course of the pressure increase or the pressure change depends in particular on the flow velocity of the volume flow during the open phase and on the density of the fluid.

With the pressure sensor or with additional determination of the temperature, the density of the fluid can be determined. From the principle known single density values (density of the fuel used, and density of the air, possibly temperature-dependent determined) and the (total) density of the fluid, the proportions of air and fuel can be determined.

With the method described, the proportion of the fuel or the proportion of the fuel originating from the filter can be determined, this proportion being determined already upstream of the combustion chamber. Thus, the fuel addition of the internal combustion engine can be regulated before the combustion of the fuel.

In particular, the determination of the density in the said frequency can be carried out, so that abrupt and / or surge-like changes in the composition of the fluid can be determined and these changes taking into account regulating the fuel addition can take place.

Furthermore, an accuracy of the determination of the fuel fraction in the fluid is independent of a quality of the mixture precontrol.

It is thus possible to control the fuel addition before the combustion of the fuel, so that raw emissions can be reduced.

Furthermore, a fast triggering of the tank ventilation (or a rapid opening of the control valve) is possible, so that an increase in the amount of purging air can be achieved. The increase in the purge air volume causes the fuel stored in the filter can be better removed from the filter.

It is further proposed a motor vehicle, at least comprising an internal combustion engine with at least one combustion chamber, a tank for a convertible in the internal combustion engine fuel with a filter, a suction tube, via which at least air and the fuel can be supplied to the combustion chamber, a control valve that a at least the fuel comprehensive Volume flow from the filter to the suction pipe (along the line, in particular the first line and the second line) regulates or according to the underlying control circuit controls and a pressure sensor for measuring a pressure profile upstream of the control valve. The control valve is openable and openable by a control unit. The control unit is designed or carried out for carrying out the method already described. The control unit can thus carry out the described method or execute it during operation of the motor vehicle.

In particular, the method can also be used in internal combustion engines that are not used in motor vehicles.

The method can also be used if portions of the fluid are to be generally determined in gas-carrying lines. For this purpose, the fluid does not need to be supplied to an internal combustion engine.

Furthermore, the method can also be executed by a computer or with a processor of a control unit.

Accordingly, there is also proposed a data processing system comprising a processor adapted / configured to perform the method or part of the steps of the proposed method.

A computer-readable storage medium may be provided that includes instructions that, when executed by a computer / processor, cause it to perform the method or at least part of the steps of the proposed method.

The statements relating to the method are transferable in particular to the motor vehicle or the computer-implemented method, and vice versa.

In addition, a use of the inventively determined density of the fluid comprising air and fuel for (direct or indirect) control proposed a fuel quantity addition to an internal combustion engine. Other particularly advantageous uses and possible uses of the determined fuel-air mixture for controlling the combustion processes, in particular in motor vehicles, will be apparent from the further explanations of the method specified here.

By way of precaution, it should be noted that the numerical terms used here ("first", "second",...) Primarily (only) serve to distinguish a plurality of similar objects, variables or processes, ie in particular no dependence and / or order of these objects, quantities or mandate processes to one another. If a dependency and / or order are required, this is explicitly stated here or it obviously results for the person skilled in the art when studying the concretely described embodiment.

Fig. 1:

ein Kraftfahrzeug; und

Fig. 2:

eine Ausführungsvariante des Verfahrens.

The invention and the technical environment will be explained in more detail with reference to the accompanying figures. It should be noted that the invention should not be limited by the stated embodiments. In particular, unless explicitly stated otherwise, it is also possible to extract partial aspects of the facts explained in the figures and to combine them with other components and findings from the present description. In particular, it should be noted that the figures and in particular the illustrated proportions are only schematic. Show it:

Fig. 1:

a motor vehicle; and

Fig. 2:

an embodiment of the method.

Fig. 1 shows a motor vehicle 11. The motor vehicle 11 includes an internal combustion engine 7 with a plurality of combustion chambers 12, a tank 5 for a convertible in the internal combustion engine 7 fuel 10 with a filter 4, a suction pipe 6, on the at least air and the fuel 10 toward Combustion chamber 12 can be supplied, and a control valve 1, which comprises a at least the fuel 10 comprehensive volume flow 2 of the fluid 3 from the filter 4 via the lines 16, 17 to the suction pipe 4 controls. The control valve 1 can be controlled by a control unit 14 for opening and closing. The control unit 14 is designed or carried out for carrying out the method.

The motor vehicle 11 further comprises a pressure sensor 13 immediately upstream of the control valve 1, via which the pressure 18 and the pressure curve 9 upstream of the control valve 1 can be measured.

The fuel 10 is stored in a tank 5, wherein fuel vapors can reach the filter 4 via the first line 16. The temporarily stored in the filter 4 fuel 10 is transferred via the control valve 1 and via the second line 17 to the intake manifold 6.

Fig. 2 shows an embodiment of the method in a diagram. On the vertical axis of the pressure 18 is applied, which is measured via the pressure sensor 13 (immediately) upstream of the control valve 1. The time 15 is plotted on the horizontal axis.

According to step a), a closing operation 8 of the control valve 1 is performed. According to step b), the pressure curve 9 upstream of the control valve 1 is measured. According to step c), a density of the fluid 3 is determined.

The control valve 1 is clocked with a frequency and opens and closes in frequency (here, the frequency is 10 hertz). The method is performed here at four consecutive closing operations 8.

During the open phase 19 of the control valve 1, a flow of the fluid 3 is formed. If the control valve 1 then closes (closing operation 8, transition to the closed phase 20), the volume flow 2 of the fluid 3 is interrupted abruptly. This leads to a measurable increase in pressure upstream of the control valve 1. The course of the pressure rise (ie the pressure curve 9) or the pressure change (or the measured pressure difference 21) depends on the flow velocity of the volume flow 2 during the open phase 19 and from the density of the fluid 3 from. The illustrated vibration of the pressure curve 9 represents the pressure change upstream of the control valve 1, which is caused by the closing operation 8.

With the pressure sensor 13 or with additional determination of the temperature, the density of the fluid 3 can be determined. The proportions of air and fuel 10 can be determined from the basically known single density values (density of the used fuel 10, and density of the air, possibly temperature-dependent) and the determined (total) density of the fluid 3.

With the method described, the proportion of the fuel 10 or the proportion of the fuel 10 originating from the filter 4 can be determined, this proportion being determined already upstream of the combustion chamber 12. Thus, the fuel addition of the internal combustion engine 7 can be regulated even before the combustion of the fuel 10.

LIST OF REFERENCE NUMBERS

1

control valve

2

flow

3

fluid

4

filter

5

tank

6

suction tube

7

Internal combustion engine

8th

closing

9

pressure curve

10

fuel

11

motor vehicle

12

combustion chamber

13

pressure sensor

14

control unit

15

Time

16

first line

17

second line

18

pressure

19

Open phase

20

Closed phase

21

pressure difference

Claims (10)

Method for controlling a control valve (1), wherein the control valve (1) controls a volume flow (2) of a fluid (3) along a line (16, 17); the method comprising at least the following steps: a) performing a closing operation (8) of the control valve (1); b) measuring a pressure curve (9) upstream of the control valve (1); c) determining a density of the fluid (3). Method according to claim 1, wherein in a further step i) the volumetric flow (2) of the fluid (3) flowing via the at least partially open regulating valve (1) is determined. Method according to claim 2, wherein in knowledge of density and volume flow (2) at least a first portion of a first component of the fluid (3) and a second portion of a second component of the fluid (3) is determined. The method of claim 3, wherein the first component is air and the second component is a fuel (10). Method according to one of the preceding claims, wherein in a further step ii) a temperature of the fluid (3) is determined, wherein the density of the fluid (3) is determined in knowledge of the temperature. Method according to one of the preceding claims, wherein the control valve (1) opens and closes at a predefinable frequency; wherein at least steps a) to c) are carried out during at least two consecutive closing operations (8). A method according to claim 6, wherein the frequency is between 5 and 50 hertz. Method according to one of the preceding claims, wherein the control valve (1) regulates the volume flow (2) of a fluid (3) from a filter (4) of a tank (5) to a suction pipe (6) of an internal combustion engine (7); wherein a control of a fuel addition of the internal combustion engine (7) is performed depending on the specific density of the fluid. Motor vehicle (11), at least comprising an internal combustion engine (7) with at least one combustion chamber (12), a tank (5) for a convertible in the internal combustion engine (7) fuel (10) with a filter (4), a suction pipe (6) , via which at least air and the fuel (10) can be supplied to the combustion chamber (12), a control valve (1) that at least the fuel (10) comprising the volume flow (2) from the filter (4) to the suction pipe (6 ) and a pressure sensor (13) for measuring a pressure curve (9) upstream of the control valve (1); wherein the control valve (1) for opening and closing is controlled by a control unit (14); wherein the control unit (14) is arranged to carry out a method according to one of the preceding claims. Use of a density of the fluid, determined according to one of claims 1 to 7, comprising air and fuel for regulating a fuel quantity addition to an internal combustion engine (7).

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