DE102014218819A1 - Method for monitoring a high-pressure pump - Google Patents

Abstract

A method for monitoring a high-pressure pump (28) of a fuel supply system (10), such a fuel supply system (10) and an arrangement for carrying out the method are presented. In the method, a signal of a pressure sensor (26) is evaluated in order to detect and evaluate effects of the high-pressure pump (28) on the admission pressure in a low-pressure region (12) and thus to determine a content of fuel vapor in the high-pressure pump (28).

Description

The invention relates to a method for monitoring a high-pressure pump in a fuel supply system of an internal combustion engine and to a fuel supply system which is set up to carry out the method.

State of the art

Internal combustion engines are heat engines that convert the chemical energy of a fuel into mechanical energy via a combustion process. Internal combustion engines used in motor vehicles are also referred to as internal combustion engines. The combustion takes place in combustion chambers, which are also referred to as cylinders.

In internal combustion engines, fuel supply systems are used to deliver fuel from a fuel tank by means of a fuel pump to a high pressure pump, which in turn pumps the fuel under high pressure into a fuel tank or rail. Pressurized fuel from this rail is then injected with injectors into the combustion chambers, the cylinders, of the engine. A distinction is made between the low-pressure region in which the fuel pump is arranged and the high-pressure region in which the rail is provided. The high pressure pump represents the transition from the low pressure area to the high pressure area.

Different methods of fuel injection are known. In the following, the gasoline direct injection (BDE) is considered, in which the fuel is injected directly into the combustion chamber. In this injection systems with demand control or control are known, the fuel pressure is adjusted to the operating point. It is necessary, especially at high fuel temperatures or in the hot start to raise the operating pressure to avoid steam formation. In addition to the provision for component scattering in the fuel supply system, provision must also be made for different fuels with different vapor pressures. In order to reduce these predictions, the fuel admission pressure is temporarily reduced during adaptation phases for test purposes until the signal from the high-pressure sensor detects pressure drops. These pressure drops are caused by increased fuel vapor content in the high-pressure pump. Subsequently, the fuel pressure is increased again so far that in normal operation no steam can occur.

Disclosure of the invention

Against this background, a method having the features of claim 1, a fuel supply system according to claim 8 and an arrangement for carrying out the described method according to claim 10 are presented. Embodiments result from the dependent claims and the description.

In the described method, it is provided to obtain early conclusions about the occurrence of steam in the high-pressure pump, in particular in adaptation phases, with the aid of a low-pressure fuel sensor, and thus to optimize the method according to which the pilot fuel pressure is reduced in adaptation phases.

The invention provides for the signal of a pressure sensor in the low-pressure region, for example the signal of the admission pressure sensor, to be evaluated and thus to draw conclusions about the presence of steam in the high-pressure pump.

There is thus an evaluation of the content of fuel vapor in the high-pressure pump on the basis of the behavior of a pressure sensor in the low-pressure region.

• – eine Vermeidung bzw. Reduktion von Dampf in der Hochdruckpumpe, insbesondere während der Adaptionsphasen, wird erreicht,
• – eine Verringerung des Verschleißes der Hochdruckpumpe ist zu erreichen,
• – es sind ggf. häufigere Adaption möglich,
• – es ist eine Erkennung der Kraftstoffqualität bzw. des Verdampfungsverhalten des aktuell vorliegenden Kraftstoffs möglich,
• – eine Reduktion von Vorhalten beim Kraftstoffvordruck kann erreicht werden,
• – eine Reduktion der elektrischen Leistung der Kraftstoffpumpe kann erreicht werden,
• – eine Reduktion des Kraftstoffverbrauchs und des CO₂-Ausstoßes ist zu erreichen.

The presented method has, at least in some of the embodiments, a number of advantages:

• An avoidance or reduction of steam in the high-pressure pump, in particular during the adaptation phases, is achieved,
• A reduction of the wear of the high-pressure pump can be achieved
• - if necessary, more frequent adaptation is possible
• It is possible to detect the fuel quality or the vaporization behavior of the currently available fuel,
• A reduction of fuel supply presuppositions can be achieved
• A reduction of the electric power of the fuel pump can be achieved
• - A reduction of fuel consumption and CO ₂ emissions can be achieved.

More accurate detection of the fuel vaporization behavior provides further benefits. Thus, an indication of ethanol content sensing in FlexFuel systems, i. H. Systems that can run on different types of fuel can be obtained either for ethanol content determination or to diagnose an ethanol sensor. Furthermore, a tank venting strategy can be optimized by more accurate modeling of the AKF load (ACF: Activated Carbon Filter) and a more accurate prioritization of the need for ACF purge phases.

Furthermore, a faster opening of the tank-venting valve (TEV) and thus, if necessary, a shortening of the tank venting phases becomes possible. In individual cases, further auxiliary measures, such as, for example, the use of an HC sensor (HC: hydrocarbons), can be avoided.

Further advantages and embodiments of the invention will become apparent from the description and the accompanying drawings.

It is understood that the features mentioned above and those yet to be explained below can be used not only in the respectively specified combination but also in other combinations or alone, without departing from the scope of the present invention.

Brief description of the drawings

1 shows an embodiment of a fuel supply system.

2 shows an adaptation curve in a graph.

Embodiments of the invention

The invention is schematically illustrated by means of embodiments in the drawings and will be described in detail below with reference to the drawings.

1 shows an embodiment of a fuel supply system, the whole with the reference numeral 10 is designated. This includes a low pressure area 12 and a high pressure area 14 , The illustration shows a fuel pump 16 , in particular an electric fuel pump, a fuel filter 18 , a sensor 20 , a pressure relief valve 22 , an electronic pump control unit 24 , a pressure sensor 26 , in this case a form pressure sensor, a high-pressure pump 28 , a rail 30 with a high pressure sensor 32 , a relay 34 with a first entrance 36 for connecting terminal 15 and a second entrance 38 for connecting the supply voltage, which is provided in particular by a battery, and an engine control unit 40 , In the engine control unit 40 is a software 42 filed for carrying out the presented method.

The engine control unit 40 controls the relay 34 and the electronic pump module 24 on, for example by means of PWM signals. Furthermore, it captures data or information from the pressure sensor 26 and the high pressure sensor 32 ,

In the process is via the fuel pump 16 the pressure gradually or continuously reduces and at the same time the signal or the course of the signal, the pressure sensor 26 delivers, evaluates. In the signal or its course effects of the high-pressure pump 28 or effects due to the operation of the high-pressure pump on the pressure or the pressure curve in the low pressure range 12 recorded and evaluated. In this way, the content of fuel vapor in the high-pressure pump, in particular taking into account the vapor pressure curve, closed.

2 shows in a graph different gradients over time. A first turn 100 shows the course of the setpoint of the pilot fuel pressure. This is lowered gradually. A second turn 102 shows the fuel pressure upstream of the high pressure pump. A third turn 104 shows the course of the fuel pressure in the low pressure area near the EKP (reference numeral 16 in 1 ). A fourth curve 106 shows the signal of the high pressure sensor.

The signal passing through the second curve 102 is evaluated in the presented method. In this case, amplitude profiles and / or frequencies of this signal can be evaluated. In this way, effects of the high-pressure pump on the admission pressure in the low-pressure range can be detected and evaluated and thus a content of fuel vapor in the high-pressure pump can be determined. In this way, it is possible to timely detect too high a content of fuel vapor in the high-pressure pump and initiate countermeasures, if necessary. Alternatively or additionally, the signal passing through the third curve 104 is represented, are evaluated in the presented method.

The method can be carried out at regular time intervals or always after certain events, for example a refueling.

For adaptation purposes, the setpoint of the pilot fuel pressure (first curve 100 ) is gradually lowered until the signal from the high-pressure sensor shows a break-in (fourth curve) 106 ).

The figure also shows that the pre-pressurized fuel pressure upstream of the high-pressure pump (second curve 102 ) already earlier, ie at a lower reduction of the pilot fuel pressure, has a reduced fluctuation range of the signal. These lower fluctuations can be explained by vapor bubbles in the high-pressure pump, which lead to reduced pulsations in the form. With this form, the high-pressure pump still manages to build up the desired high pressure. The signal of the high-pressure sensor is (still) constant.

By means of the pressure sensor in the low-pressure range, the first occurrence of steam in the high-pressure pump can thus be more accurately derived and thus possible component damage avoided. For this purpose, the pressure readings of the pressure sensor in the low-pressure region must be suitably detected and analyzed for the fluctuation range or another suitable variable. If it falls below a threshold value, the adaptation is then interrupted and serves as a measure of the present vapor pressure of the fuel. If the adaptation is performed at several operating points, such as at different temperatures, the vapor pressure curve of the fuel present can be estimated.

As a pressure sensor, a pre-pressure sensor can be used, which is assigned to the fuel pump. Usually, this is present anyway, so that no additional component is required.

By the more accurate recognition of the evaporation behavior can be further systemic advantages, such. B. an optimization of the tank ventilation strategy and obtaining a hint or indices for ethanol content determination achieve.

The presented method can be used in all vehicles with gasoline direct injection. The conditions for regulated or controlled fuel supply systems are particularly favorable, in particular if a fuel pressure sensor in the low-pressure region is installed anyway.

Claims (10)

Method for monitoring a high-pressure pump ( 28 ) in a fuel supply system ( 10 ) of an internal combustion engine, which has a low-pressure region ( 12 ) and a high pressure area ( 14 ) and a fuel pump ( 16 ) and a high pressure pump ( 28 ), wherein a pressure sensor ( 26 ) which provides a signal indicative of a pre-pressure in the low-pressure region ( 12 ) of the fuel supply system ( 10 ), wherein the signal of the pressure sensor ( 26 ) is evaluated for the effects of the high-pressure pump ( 28 ) to the admission pressure in the low-pressure area ( 12 ) to detect and evaluate a content of fuel vapor in the high-pressure pump ( 28 ) to investigate. Method according to Claim 1, in which a pressure sensor ( 26 ) a form sensor is used, which is assigned to the fuel pump. Method according to Claim 1 or 2, in which pressure pulsations generated by the high-pressure pump ( 28 ) are evaluated in the course of the signal.  Method according to Claim 3, in which amplitude profiles and frequencies in the signal are evaluated.  Method according to one of claims 1 to 4, which is carried out for adaptation purposes.  Method according to one of claims 1 to 5, which is carried out after refueling. Method according to one of claims 1 to 6, which is used to determine a fuel type. Fuel supply system for a motor vehicle, in particular for carrying out a method according to one of Claims 1 to 7, which has a low-pressure region (US Pat. 12 ) and a high pressure area ( 14 ) and a fuel pump ( 16 ) and a high pressure pump ( 28 ), wherein a pressure sensor ( 26 ) providing a signal indicative of a pre-pressure in a low-pressure region ( 12 ) of the fuel supply system ( 10 ), wherein the fuel supply system ( 10 ) is adapted to the signal of the pressure sensor ( 26 ) to assess the effects of the high-pressure pump ( 28 ) to the admission pressure in the low-pressure area ( 12 ) to detect and evaluate a content of fuel vapor in the high-pressure pump ( 28 ) to investigate. Fuel supply system according to Claim 8, in which a pressure sensor ( 26 ) a pre-pressure sensor, the fuel pump ( 16 ) is assigned. Arrangement for monitoring a high-pressure pump ( 28 ) in a fuel supply system ( 10 ) of an internal combustion engine, which has a low-pressure region ( 12 ) and a high pressure area ( 14 ) and a fuel pump ( 16 ) and a high pressure pump ( 28 ), wherein a pressure sensor ( 26 ) providing a signal indicative of a pre-pressure in the low-pressure region ( 12 ) of the fuel supply system ( 10 ), wherein the arrangement is adapted to the signal of the pressure sensor ( 26 ) to assess the effects of the high-pressure pump ( 28 ) to the pressure in the low pressure range ( 12 ) to detect and evaluate a content of fuel vapor in the high-pressure pump ( 28 ) to investigate.

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