DE102016221868A1 - Method for controlling a tank ventilation for a fuel tank by means of adaptation of an air mass - Google Patents

Abstract

The invention relates to a method for controlling a tank ventilation for a fuel tank, which is connected via at least one line with an internal combustion engine, in which / at least one tank vent valve is arranged, wherein cylinders (60, 61, 62, 63) of the internal combustion engine are individually filled , The method comprises the following steps: Initially, a regulation (101) of a provisional injection quantity (mv) individually available in each cylinder (60, 61, 62, 63) takes place so that the preliminary injection quantity (mv) for each cylinder ( 60, 61, 62, 63) is the same. Then, combustion air ratios are detected individually for each cylinder (60, 61, 62, 63) and a deviation of an air mass (mu) for each cylinder (60, 61, 62, 63) from the combustion air ratios (λ) is determined. This is followed by a control (102) of the at least one tank venting valve so that the air mass (mt) is adapted for each cylinder (60, 61, 62, 63) and is the same for each cylinder (60, 61, 62, 63). Thereupon, an injection mass (me) increased by the tank vent, which is additionally injected individually into each cylinder (60, 61, 62, 63), is detected and finally an adaptation (103) of the actual injection mass (mt) containing the preliminary injection mass ( mv) and the increased injection mass (me) comprises, performed to a desired injection mass.

Description

The present invention relates to a method of controlling a tank vent for a fuel tank by adjusting an air mass for each cylinder of an internal combustion engine. Furthermore, the present invention relates to a computer program that executes each step of the method when running on a computing device and to a machine-readable storage medium that stores the computer program. Finally, the invention relates to an electronic control device which is set up to carry out the method.

State of the art

To comply with evaporative emission limits fuel tanks of motor vehicles have a tank ventilation system. This comprises an activated carbon filter for adsorbing the fuel vapors escaping from a vent line of the fuel tank and at least one line which connects the activated carbon filter with a suction pipe of an internal combustion engine. In this / -n line (s) at least one tank vent valve is arranged.

Fuel vapors escaping from the fuel tank are adsorbed in the activated carbon filter, so that only purified air can escape into the atmosphere. In order to regenerate the activated carbon again and again, the adsorbed fuel vapors are passed in a regeneration operation in the intake manifold of the internal combustion engine. In the suction pipe, a negative pressure prevails, so that when the tank vent valve is open, a negative pressure is also generated in the line and in the activated carbon filter. As a result, air from the environment flows through the activated carbon into the intake manifold. This desorbs the adsorbed hydrocarbons and leads them to engine combustion. The tank vent valve in the connection line meters this regeneration flow, which is also referred to as "purge flow".

Over a duty cycle, this Regenerierstrom can be adapted to the operating condition of the internal combustion engine. The amount of hydrocarbon introduced is deduced with the aid of the lambda control of the internal combustion engine, and the amount of fuel injected via a fuel injector into the internal combustion engine is correspondingly adapted via a mixture adaptation.

From the DE 10 2012 222 101 A1 For example, a method of controlling a direct injection internal combustion engine is known. In this case, an injected fuel mass for all injection valves of all cylinders of the internal combustion engine is assimilated. Thereafter, an error detection of the injected fuel mass and a supplied air mass. In one aspect, the equalization of the injectors may be accomplished by a mass error compensation.

Tank ventilation systems and corresponding methods are known in which the regeneration flow is distributed uniformly over all the cylinders. In such a tank ventilation system, a plurality of connecting lines are provided, which connect the activated carbon filter individually to each of the cylinders and in each of which a separate tank ventilation valve is arranged. Now, the regenerating current can be divided individually to all cylinders via a suitable control of the tank ventilation valves.

In addition, a tank ventilation system is known in which a suction-synchronous activation of the tank ventilation valve takes place. That is, each time an intake valve for one of the cylinders is opened, the tank vent valve is opened accordingly. This also ensures that the Regenerierstrom evenly distributed to all cylinders. In addition, the tank venting valve can be operated "rolling", so that, taking into account the time of flight in each case a different cylinder is supplied with gaseous hydrocarbon. In addition, a second connecting line between the activated carbon filter and the intake manifold may be provided, in which a tank ventilation valve is likewise arranged. Now, the suction-synchronous control can be extended to both tank-venting valves to cover a larger speed range.

Disclosure of the invention

The method relates to a tank ventilation for a fuel tank, which is connected via at least one line to an internal combustion engine. In particular, each cylinder of the internal combustion engine is assigned a line, in each of which a tank ventilation valve is arranged. Alternatively, a line in which a tank vent valve is arranged, which is actuated asynchronously be provided. As a result, the cylinders of the internal combustion engine are individually filled with gaseous hydrocarbons from the tank ventilation.

In this procedure, tank venting is controlled by the following steps. Initially, a provisional injection mass of fuel individually available in each cylinder is adjusted so that the preliminary injection mass for each cylinder is the same. Subsequently, combustion air conditions are detected individually for each cylinder, preferably by at least one lambda probe. The combustion air ratio indicates the ratio of an actual air mass to an air mass necessary for complete combustion. In the following, a deviation of the air masses between the cylinders is determined from the combustion air ratio assigned to it.

In a further step, the at least one tank-venting valve is activated so that the air mass for each cylinder is adjusted so that it is the same for each cylinder. In other words, the tank venting valve (s) is / are controlled so that the air mass originating from the tank venting is distributed among the cylinders so that it is the same for each cylinder. However, gaseous hydrocarbons also flow from the tank ventilation into the cylinders with the air mass, which in turn would change the injection mass. Therefore, the increased by the tank ventilation injection mass, which is additionally injected individually into each cylinder, detected and finally the actual injection mass, which includes the preliminary injection mass and the increased injection mass, adapted to a desired injection mass. As a result, a change in the actual injection mass of the fuel is taken into account and compensated due to the increased by the tank ventilation injection mass. As a result, in addition to a wrongly metered injection mass, especially a rough running of the engine can be reduced. Furthermore, the exhaust gas influence can be minimized and the combustion ability of the internal combustion engine can be increased.

According to one aspect, the detection of the increased injection mass takes place by means of combustion air ratios which are individually re-detected for each cylinder. Against this background, no additional sensors are required in the system.

According to a further aspect, the detection of the increased injection mass takes place by means of a recognition of the rough running individually for each cylinder. As pointed out above, this method offers the advantage of reducing the uneven running. Therefore, it is advantageous to directly recognize the effects of the process on the uneven running and to use as parameters for the increased injection mass.

The preliminary injection mass can preferably be regulated by means of Controlled Valve Operation (CVO). In CVO, the actual open time of the injector is determined and compared to a setpoint. As soon as a deviation of the actual open time from the setpoint is detected, an adjustment function is activated in order to correct the injection mass and to reduce measurement tolerances in the injection mass. As injection system, both a (gasoline) direct injection and a (gasoline) intake manifold injection can be used. It should be noted that the CVO can be used in both injection systems. The CVO offers the advantage of regulating the preliminary injection mass for all cylinders with high accuracy.

Furthermore, the air mass in the cylinders can preferably be varied via the at least one tank-venting valve and via at least one throttle flap of at least one intake manifold. The cylinders are initially filled with air from the intake manifold. This part of the air mass is not affected by gaseous hydrocarbon. If the at least one tank vent valve is used to vary the air mass in the cylinders, the proportion of air used from the tank vent can be increased by operating at a higher purge rate thereby increasing the regeneration capability of the tank vent.

The computer program is set up to perform each step of the method, especially when executed on a computing device or electronic controller. It allows the implementation of the method on an electronic control unit, without having to make any structural changes. For this purpose, the computer program is stored in particular on the machine-readable storage medium.

When the computer program is loaded on an electronic control unit, the electronic control unit is set up, which is set up to control the tank ventilation for the fuel tank by means of the method.

list of figures

• 1 zeigt ein Tankentlüftungssystem, das durch mehrere Regenerationsleitungen, in denen jeweils ein Tankentlüftungsventil angeordnet ist, mit Zylindern einer Verbrennungsmaschine verbunden ist und mit einem Ausführungsbeispiel des erfindungsgemäßen Verfahrens gesteuert werden kann.
• 2 zeigt ein weiteres Tankentlüftungssystem, bei dem die Ansteuerung des einen in einer Regenerationsleitung angeordneten Tankentlüftungsventils saugsynchron mit Zylindern einer Verbrennungsmaschine erfolgt und das mit einem Ausführungsbeispiel des erfindungsgemäßen Verfahrens gesteuert werden kann.
• 3 zeigt ein Ablaufdiagramm eines Ausführungsbeispiels des erfindungsgemäßen Verfahrens.

Embodiments of the invention are illustrated in the drawings and explained in more detail in the following description.

• 1 shows a tank ventilation system, which is connected by a plurality of regeneration lines, in each of which a tank vent valve is arranged, with cylinders of an internal combustion engine and can be controlled with an embodiment of the method according to the invention.
• 2 shows a further tank ventilation system, in which the control of the one arranged in a regeneration pipe tank venting valve is carried out synchronously with cylinders of an internal combustion engine and which can be controlled with an embodiment of the method according to the invention.
• 3 shows a flowchart of an embodiment of the method according to the invention.

Embodiment of the invention

In 1 schematically a tank ventilation system of a vehicle is shown, in which the inventive method is used. In a fuel tank 10 there is fuel. Above the liquid fuel form gaseous hydrocarbons, which are an activated carbon filter 20 via a vent line 11 be supplied. From the activated carbon filter 20 lead several regeneration lines 30 . 31 . 32 . 33 to an internal combustion engine 50 , In every government administration 30 . 31 . 32 . 33 each is a tank vent valve 40 . 41 . 42 . 43 arranged, which a mass flow of the hydrocarbon gas and the air through the respective Regerationsleitung 30 . 31 . 32 . 33 regulated. In this embodiment, the internal combustion engine 50 For clarity, four cylinders 60 . 61 . 62 . 63 on, with the four cylinders 60 . 61 . 62 . 63 with a common intake manifold 51 are connected, which branches to the cylinders out. From the suction pipe 51 Air is sucked from the environment, which is an air filter 53 , a charge air cooler 54 and a throttle 52 happens before in injectors, not shown in the cylinder 60 . 61 . 62 . 63 arrives. Every cylinder 60 . 61 . 62 . 63 is one of the regeneration lines 30 . 31 . 32 . 33 assigned downstream of the branches on the respective cylinder 60 . 61 . 62 . 63 in the intake manifold 51 lead. The hydrocarbon gas eventually becomes the internal combustion engine 50 fed, where it is then burned.

In this embodiment, the mass flow of the hydrocarbon gas and the air from the tank vent for each cylinder 60 . 61 . 62 . 63 individually by means of the associated tank venting valve 40 . 41 . 42 . 43 Regulated, with the tank ventilation valves 40 . 41 . 42 . 43 from an electronic control unit connected thereto 80 is controlled.

The electronic control unit 80 is also equipped with a lambda sensor 70 connected, which determines a combustion air ratio λ. The combustion air ratio λ (also called the air ratio or colloquially lambda value) indicates the ratio of an actual air mass m _L t to an air mass m _L n necessary for complete combustion and is calculated according to formula 1: $$\mathrm{\lambda }=\frac{{\text{m}}_{\text{L}}\text{t}}{{\text{m}}_{\text{L}}\text{n}}$$

The lambda probe 70 may vary depending on the operating conditions of the internal combustion engine 50 a total combustion air ratio λ _{ges of} all cylinders 60 . 61 . 62 . 63 or a single combustion air ratio λ _e individually for each cylinder 60 . 61 . 62 . 63 determine. The latter is realized, for example, by the lambda probe 70 the combustion air ratios λ synchronous to successive work cycles of the cylinder 60 . 61 . 62 . 63 determined.

In 2 schematically another tank ventilation system of a vehicle is shown, in which the inventive method is used. The same components are identified by the same reference numerals, so that their description to the above description to 1 is referenced. Unlike the tank ventilation system off 1 , this tank ventilation system has a regeneration line 34 on, the upstream of the junction in the intake manifold 51 empties. Accordingly, the mass flow of the hydrocarbon gas and the air from the tank vent for all cylinders 60 . 61 . 62 . 63 together through the individual, in the regeneration line 34 arranged tank vent valve 44 regulated. This tank vent valve 44 is from the electronic control unit 80 in synchrony with the cylinders 60 . 61 . 62 . 63 driven. At the same time, the tank ventilation valve becomes 30 , every time you open the injector for one of the cylinders 60 . 61 . 62 . 63 , opened accordingly. Under certain operating conditions, the tank vent valve becomes 44 Operated "rolling", so taking into account the flight time in each case a different cylinder 60 . 61 . 62 . 63 is acted upon by fuel vapors.

3 shows a flowchart of an embodiment of the method according to the invention. In a starting state 100 are an unregulated air mass m _L u passing through the throttle 52 from the suction pipe 51 and an unregulated injection mass m _K u of the fuel for each of the cylinders 60 . 61 . 62 . 63 different. Only one injection time t _{i of} the injection valve is for all cylinders 60 . 61 . 62 . 63 the same regulated, but not an open time t _o in which the injection valve is actually open. This results in a constant total combustion air ratio λ _ges , whereas the individual combustion air ratios λ _e corresponding to each cylinder 60 . 61 . 62 . 63 are different, so that a high running noise LU results.

According to the procedure becomes a regulation 101 one in each cylinder 60 . 61 . 62 . 63 individually available provisional injection mass m _k v performed, so that the provisional injection mass m _k v for each cylinder 60 . 61 . 62 . 63 is equal to. The regulation 101 takes place by means of a controlled valve operation, in which the actual open time t _{o of} the injection valve is determined and compared with a desired value. As soon as a deviation of the actual open time t _o from the setpoint is detected, an adjustment function is activated to correct the injection mass. Here, the open time t _{o of} the injection valves for all cylinders 60 . 61 . 62 . 63 adjusted, whereby, however, the injection time t _{i of} the injectors changed individually. Detection of the individual combustion air ratios λ _e becomes individual for each cylinder 60 . 61 . 62 . 63 carried out, and from these individual combustion air ratios λ _e, a deviation of the unregulated air masses m _L u between each of the cylinders 60 . 61 . 62 . 63 determined. It should be noted here that the combustion air ratio λ according to formula 1 is calculated from an actual air mass m _L t. At this point, however, the actual air mass m _L t corresponds to the unregulated air mass m _L u, so that it is used for the detection of the individual combustion air ratios λ _e .

By means of the deviations of the uncontrolled air masses m _L u becomes a control 102 the tank vent valves 40 . 41 . 42 . 43 (in the case of the tank ventilation system off 1 ) or the tank venting valve 44 (in the case of the tank ventilation system off 2 ) and the throttle 52 of the suction pipe 51 carried out so that the cylinders 60 . 61 . 62 . 63 in each case an increased air mass m _L e in addition to the unregulated air mass m _L u is applied. Accordingly, t is an actual air mass m _L, which is calculated from now on as the sum of unregulated air mass m _L u and the increased air mass m e _L, for all the cylinders 60 . 61 . 62 . 63 equal. As with the air also gaseous hydrocarbons from the activated carbon filter 20 the tank ventilation via the regeneration pipe (s) 30 . 31 . 32 . 33 . 34 in the cylinders 60 . 61 . 62 . 63 However, an actual injection mass m _K t, which is calculated as the sum of the provisional injection masses m _k v and the increased injection mass m _K e, changes as a result of this and results in an increased injection mass m _K e as fuel. These increased injection masses m _K e are below for each cylinder 60 . 61 . 62 . 63 detected by again their individual combustion air ratios λ _{e are} determined. In a further exemplary embodiment, the increased injection masses m _K e are detected by a recognition of the uneven running LU individually for each cylinder 60 . 61 . 62 . 63 he follows.

Finally, an adjustment takes place 103 the actual injection mass m _K t to a desired injection mass. For this purpose, the provisional injection mass m _k v for each cylinder 60 . 61 . 62 . 63 reduced by the amount of increased injection masses m _K e, so that the actual injection masses m _K t for all cylinders 60 . 61 . 62 . 63 are constant. In this case, the open time t _{o of} the injection valves is changed. Through this adaptation 103 Both the total combustion air ratio λ _ges and the individual combustion air ratios λ _{e is} constant. As a result of the actual balanced air mass m _L t and the balanced actual injection amount m _L t, the rough running LU is significantly improved and over all cylinders 60 . 61 . 62 . 63 constant.

QUOTES INCLUDE IN THE DESCRIPTION

This list of the documents listed by the applicant has been generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Cited patent literature

• DE 102012222101 A1 [0005]

Claims (8)

Method for controlling a tank ventilation for a fuel tank (10), which is connected via at least one line (30, 31, 32, 33, 34) to an internal combustion engine (50) in which at least one tank ventilation valve (40, 41, 42 , 43, 44), wherein cylinders (60, 61, 62, 63) of the internal combustion engine (50) are individually filled, comprising: - regulating (101) one in each cylinder (60, 61, 62, 63) individually available, preliminary injection mass (m _K v) so that the provisional injection mass (m _K v) is the same for each cylinder (60, 61, 62, 63); - Detecting combustion air ratios (λ _e ) individually for each cylinder (60, 61, 62, 63); - Determining a deviation of air masses (m _L u) between the cylinders (60, 61, 62, 63) from the combustion air ratios (λ _e ); - control (102) of the at least one tank vent valve (40, 41, 42, 43, 44), so that the air mass (m _L t) for each cylinder (60, 61, 62, 63) is adjusted so that they for each cylinder (60, 61, 62, 63) is the same; - detecting an increased by the tank ventilation injection mass (m _K e), which is additionally injected individually into each cylinder (60, 61, 62, 63); and - adaptation (103) of the actual injection mass (m _K t), which comprises the provisional injection mass (m _K v) and the increased injection mass (m _K e), to a desired injection mass. Method according to Claim 1 Characterized in that the detection of increased injection mass (m _K e) means for each cylinder (60, 61, 62, 63) individually again detected combustion air ratios (Ae) is carried out. Method according to Claim 1 , characterized in that the detection of the increased injection mass (m _K e) by means of a detection of a rough running (LU) takes place individually for each cylinder (60, 61, 62, 63). Method according to one of the preceding claims, characterized in that the regulation (101) of the provisional injection mass is effected by means of controlled valve operation. Method according to one of the preceding claims, characterized in that the air mass (m _L u) via the at least one tank vent valve (40, 41, 42, 43, 44) and at least one throttle valve (52) at least one suction pipe (51) is varied , Computer program, which is set up, each step of the procedure according to one of Claims 1 to 5 perform. Machine-readable storage medium on which a computer program is based Claim 6 is stored. An electronic control unit (80) arranged to operate by the method of any one of Claims 1 to 5 to control the tank vent for a fuel tank (10).

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