EP1262659B1 - Fuel system for an internal combustion engine - Google Patents

Description

State of the art

The invention relates to a fuel system according to the preamble of claim 1 and an internal combustion engine and a method for operating an internal combustion engine according to the independent claims.

From the DE 195 39 883 A1 For example, a fuel system is known in which two pumps connected in series deliver the fuel from a fuel tank to a fuel rail, commonly referred to as a "rail". In the fuel rail, the fuel is stored under relatively high pressure. To the fuel rail injection valves are connected, which inject the fuel directly into the corresponding combustion chambers.

The pressure in the fuel rail is controlled by a pressure valve. Depending on the control of the pressure valve, fuel is returned from the fuel manifold via a return line in the fuel tank. In the known fuel system, the pressure in the fuel rail is reduced after stopping. However, due to heat conduction from the engine block ago, it can then in the in the fuel manifold existing fuel to form vapor bubbles that make it difficult to restart the engine. In order to eliminate this disadvantage, in the known fuel system when starting the internal combustion engine, the pressure of the fuel delivered by the first of the two fuel pumps is increased in order to eliminate possibly existing vapor bubbles as quickly as possible from the fuel system. However, this takes a certain amount of time.

EP 1 092 863 A2 discloses a pressure control valve for a fuel system, the valve element is acted upon by a spring in the closed position. The opening pressure is relatively low and can be increased by an electromagnetic actuator. US 5,558,068 describes a solenoid valve for a fuel injection system which is opened at startup to purge vapor bubbles from a fuel rail. DE 199 36 287 A1 discloses a demand control for a fuel delivery module in which a check valve maintains high pressure in a low pressure region after the engine has been shut down. US 6,024,064 describes a high-pressure fuel system with a pressure control valve, which can be additionally forcibly opened by means of an electromagnetic actuator.

The invention relates to a fuel system with the features of claim 1, and an internal combustion engine and a method with the independent claims.

Advantages of the invention

The fuel system according to the invention has the advantage that vapor bubbles can not form at all, since the pressure in the fuel manifold is maintained at a high level even when the internal combustion engine is switched off. Thus are No action is required to remove any vapor bubbles from the fuel system before restarting a hot engine. The starting of an internal combustion engine, which is equipped with the fuel system according to the invention, therefore takes place very quickly.

Maintaining the relatively high pressure in the fuel rail is very easy in the fuel system according to the invention: The valve device is constructed so that it is closed in its non-actuated rest state, so there is no connection back from the fuel rail, for example to the fuel tank. Such a non-actuated state is generally present anyway with the internal combustion engine stopped.

Electrically actuated valve devices are very simple and inexpensive to produce. A de-energized state is also easily realized when the internal combustion engine. An inventively provided biasing means may for example comprise a spring. The actuation of the valve element thus takes place against the force of the biasing device. Such a valve device is simple and works reliably. In this case, the biasing device is selected so that the valve device opens in the non-actuated, ie de-energized state when the pressure in the fuel rail exceeds a certain value. This measure ensures that the pressure in the fuel rail can not exceed a maximum value when the internal combustion engine is switched off. As a result, the reliability of the fuel rail and connected components is guaranteed, since heating of the fuel enclosed in the fuel rail, for example, due to heat conduction from the internal combustion engine and the associated expansion of the trapped fuel does not damage the fuel rail or enclosed components.

By the opening pressure of the valve device in the non-actuated state is lower than the maximum permissible operating pressure of the fuel injection device, the fact is taken into account that the usual fuel injectors from a certain pressure in the fuel rail can not be safely operated. In addition, there is the danger that when the maximum permissible operating pressure is exceeded, the fuel injection device no longer closes securely and thus fuel reaches the combustion chamber of the internal combustion engine when the internal combustion engine is stationary. All of this is prevented by the fuel system according to the invention.

In an advantageous development of the opening pressure of the valve device at high speed of the internal combustion engine is higher than at low speed of the internal combustion engine. Due to this measure, the fact is again taken into account that it is favorable for consumption and emission-optimal operation of the internal combustion engine when the pressure of the fuel at the fuel injection device at low engine speed is rather low and high at high engine speed is. The opening pressure of the valve device thus ensures a pressure corresponding to the respective operating state of the internal combustion engine in the fuel collecting line.

drawing

Fig. 1:

ein Blockschaltbild einer Brennkraftmaschine mit einem Kraftstoffsystem mit einer Ventileinrichtung;

Fig. 2:

einen teilweisen Schnitt durch die Ventileinrichtung von Fig. 1; und

Fig. 3:

ein Diagramm, in dem der Öffnungsdruck der Ventileinrichtung von Fig. 2 über der Drehzahl der Brennkraftmaschine aufgetragen ist.

Hereinafter, a preferred embodiment of the invention will be explained in detail with reference to the accompanying drawings. In the drawing show:

Fig. 1:

a block diagram of an internal combustion engine with a fuel system with a valve device;

Fig. 2:

a partial section through the valve device of Fig. 1 ; and

3:

a diagram in which the opening pressure of the valve device of Fig. 2 is plotted over the speed of the internal combustion engine.

Description of the embodiment

In Fig. 1 an internal combustion engine carries the reference numeral 10. Overall, it is symbolically indicated by a dot-dash line in the present embodiment. The internal combustion engine 10 in turn comprises a fuel system 12.

To this belongs a fuel tank 14, from which an electric fuel pump 16 delivers fuel into a fuel connection 18. Via a filter 20, the fuel reaches a high-pressure fuel pump 22. The latter is driven directly by a crankshaft of the internal combustion engine 10 in a manner not shown here. The pressure in the fuel connection 18 is adjusted by a low pressure regulator 24.

The high pressure fuel pump 22 further compresses the fuel pre-compressed by the electric fuel pump 16 and delivers it to a fuel rail 26. This is commonly referred to as a "rail". In it, the fuel is stored during operation of the internal combustion engine 10 under very high pressure, up to about 120 bar. To the fuel manifold 26 a plurality of fuel injectors 28 are connected. In the present case, these are injectors which inject the fuel directly into corresponding combustion chambers 30. The illustrated internal combustion engine 10 is therefore one with direct fuel injection. The fuel can be either gasoline or diesel.

The pressure in the fuel rail 26 is detected by a pressure sensor 32. This supplies signals to a control and regulating device 34. The fuel manifold 26 is connected to the fuel connection 18 via a fuel connection 36. In the fuel connection 36, a pressure valve 38 is arranged, the exact configuration will be explained below. The pressure valve 38 is controlled by the control and regulating device 34.

• Fig. 2 zeigt einen zylindrischen Ventilkörper 40, der in Einbaulage in eine zylindrische Ausnehmung eines in Fig. 2 nicht dargestellten Aufnahmeteils eingesetzt und an diesem befestigt ist. An diesem Aufnahmeteil sind auch die Anschlüsse für die Kraftstoffverbindung 36 vorhanden. Der zwischen dem Druckventil 38 und der Hochdruck-Kraftstoffpumpe 22 liegende Bereich der Kraftstoffverbindung trägt dabei das Bezugszeichen 36a, wohingegen der zur Kraftstoffverbindung 18 hin zeigende Bereich das Bezugszeichen 36b trägt.

The pressure valve 38 is constructed in detail as follows (see. Fig. 2 ):

• Fig. 2 shows a cylindrical valve body 40 which in the installed position in a cylindrical recess of a in Fig. 2 Not shown receiving part used and attached to this. At this receiving part and the connections for the fuel connection 36 are present. The region of the fuel connection lying between the pressure valve 38 and the high-pressure fuel pump 22 bears the reference numeral 36a, whereas the area facing the fuel connection 18 bears the reference numeral 36b.

The valve body 40 is constructed in two parts. Im in Fig. 2 lower part 42 is a valve body 40 coaxial through hole 44 is present, which in Fig. 2 flared towards the top. The conical extension (without reference numeral) forms a valve seat for a valve ball 46. Im in Fig. 2 Upper part 48 of the valve body 40 is a likewise to the valve body 40 coaxial through-hole 50 is provided, branch off from the two radial bores 52. The through-bore 44 in the lower part 42 of the valve body 40 is connected to the inlet of the pressure valve 38 and thus in the installed position with the line 36a, whereas the radial bores 52 lead to an outlet of the pressure valve 38 and thus in installation position to the line 36b.

In the central through hole 50, a valve stem 54 is arranged, at the in Fig. 2 upper end portion of a magnet armature 56 is attached. The valve stem 54 is guided in the region of the through hole 50 in a slide bush (not shown). In the upper region of the upper part 48 of the valve body 40, a sleeve 58 is mounted on the outer circumferential surface of the upper part 48, which with its in Fig. 3 upper area is in turn connected to a housing body 60. In this one is in Fig. 2 down blind hole 62 available.

At the in Fig. 2 lower end of the blind hole 62, a guide ring 64 is inserted into this. In this, the upper end 66 of the valve stem 54 is slidably guided. The upper end 66 of the valve stem 54 is acted upon by a compression spring 68, which is supported on the base of the blind hole 62 in the housing body 60. Ultimately, the valve ball 46 is pressed against the valve seat in the through hole 44 in the lower part 42 of the valve body 40 via the compression spring 68 and the valve stem 54.

On the housing body 60, a retaining ring 70 is attached outside. The retaining ring 70 projects radially from the housing body 60 and is coaxial with it as a whole. At the radially outer edge region of the retaining ring 70 two ironing elements 72 are fixed, which surround a magnetic winding 74. The upper portion of the housing body 60, the retaining ring 70 and the bracket members 72 are molded with plastic 76.

When the engine 10 is turned on, the pressure in the fuel rail 26 is detected by the pressure sensor 32 and the control valve 34, the pressure valve 38 is driven so that in the fuel rail 26 a desired pressure prevails. In this case, energization of the magnet winding 74 leads to a force acting on the armature 56 in the direction of the arrow 78 force. This is superimposed on the closing force of the compression spring 68. Thus, the valve ball 46 is pressed with energization of the magnetic winding 74 with less force against the valve seat, whereby the opening pressure of the pressure valve 38 can be varied.

If no current flows through the magnet winding 74, the valve ball 46 is pressed against the valve seat with the full force of the compression spring 68. In this case, therefore, the pressure valve 38 is closed. However, the compression spring 68 is dimensioned so that the valve ball 46 against the Force of the compression spring 68 lifts off the valve seat when the pressure in the fuel rail 26 exceeds a maximum allowable value. In this way, it is ensured that when the magnetic winding 74 can no longer be energized, for example, because the power supply is interrupted by a defect, the pressure in the fuel rail 26 does not exceed a maximum allowable value.

Thus, the reliability of the fuel injectors 28, which can work safely only up to a certain maximum pressure, guaranteed. Furthermore, it is ensured that when the internal combustion engine is shut off in the fuel volume trapped in the fuel rail 26 due to heat conduction within the fuel rail 26 can not lead to an impermissible pressure increase, which, for example, to an unwanted leakage of the fuel injectors 28 into the combustion chambers 30 could lead into it.

When the internal combustion engine 10 is turned off, the magnet winding 74 is de-energized. As already stated, in this case, the valve ball 46 is pressed with the maximum force of the compression spring 68 against the valve seat. The pressure valve 38 is thus closed and completed in the fuel manifold 26 fuel volume to the outside. The existing pressure in the fuel rail 26 is thus not deflated when the engine 10, but maintained.

By a variable energization of the magnetic winding 74, it is possible to adjust the opening pressure of the pressure valve 38 to the rotational speed of the internal combustion engine 10. For emission and consumption reasons, it is desired that the fuel pressure applied to the fuel injectors 28 is lower at low engine speeds 10 than at high engine speeds. This is normally achieved by a corresponding energization of the magnet winding 74. As a result, an opening characteristic of the pressure valve 38 can be realized, as in Fig. 3 is shown. In this case, it is ensured that the opening pressure PO of the pressure valve 38 is smaller than the maximum permissible operating pressure PV _{max of} the fuel injection devices 28.

Claims (4)

1. Fuel system for an internal combustion engine, having a fuel tank, having at least one fuel pump, having a fuel collecting line which is fed by the fuel pump, having a valve device by means of which the pressure in the fuel collecting line can be controlled, and having at least one fuel injection device via which the fuel can pass into a combustion chamber of the internal combustion engine, with the valve device being electrically actuable by means of a magnet coil and being designed so as to be closed in the de-energized state at least under normal operating pressure in the fuel collecting line, and with the valve device comprising a preload device which loads a valve element in the closing direction and is designed such that the valve device opens when the pressure in the fuel collecting line exceeds a certain value, the so-called opening pressure, characterized in that the energization of the magnet coil acts in the opening direction of the valve element, in such a way that the valve element is pressed against the valve seat with a reduced force and the opening pressure falls in the event of an energization of the magnet coil, and in that the opening pressure of the valve device in the de-energized state is lower than a maximum admissible functional pressure of the fuel injection device, in the event of the exceedance of which the fuel injection device no longer reliably closes.
2. Fuel system (12) according to Claim 1, characterized in that the opening pressure of the valve device (38) is higher at high rotational speed of the internal combustion engine (10) than at low rotational speed of the internal combustion engine (10).
3. Internal combustion engine (10), in particular for motor vehicles, which comprises a fuel system (10) having a fuel tank (14), having at least one fuel pump (16, 22), having a fuel collecting line (26) which is fed by the fuel pump (22), having a valve device (38) by means of which the pressure in the fuel collecting line (26) can be controlled, and having at least one fuel injection device (28) via which the fuel can pass into a combustion chamber (30) of the internal combustion engine (10), characterized in that the fuel system is designed according to one of Claims 1 and 2.
4. Method for operating an internal combustion engine, in particular for motor vehicles, in which method the fuel is fed from a fuel tank into a fuel collecting line by means of at least one fuel pump and from said fuel collecting line into a combustion chamber of the internal combustion engine by means of a fuel injection device, and in which method the pressure in the fuel collecting line is controlled by means of a valve device, with the valve device being electrically actuated by means of a magnet coil and being closed in the de-energized state at least under normal pressure in the fuel collecting line, and with a valve element of the valve device being loaded in a closing direction by a preload device, such that the valve device opens when the pressure in the fuel collecting line exceeds a certain value, the so-called opening pressure, characterized in that the energization of the magnet coil acts in the opening direction of the valve element, in such a way that the valve element is pressed against the valve seat with a reduced force and the opening pressure falls in the event of an energization of the magnet coil, and in that the opening pressure of the valve device in the de-energized state is lower than the maximum admissible functional pressure of the fuel injection device, in the event of the exceedance of which the fuel injection device no longer reliably closes.

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