EP1042608B1 - Fuel supply system of an internal combustion engine - Google Patents

Description

State of the art

The invention is based on a fuel supply system for supplying fuel to an internal combustion engine according to the preamble of claim 1, as e.g. out DE-A-19 630 938 is known.

So far, there have been fuel supply systems in which a first fuel pump from a fuel tank promotes fuel via a fuel connection to a second fuel pump. The second fuel pump in turn conveys the fuel into a pressure line to which at least one fuel valve is connected.
Usually, the number of fuel valves is equal to the number of cylinders of the internal combustion engine. The fuel supply system may be constructed so that the fuel valve injects the fuel directly into a combustion chamber of the internal combustion engine. During operation of this fuel supply system, a high pressure in the pressure line leading to the fuel valve is required.

The second fuel pump is usually directly from the Internal combustion engine mechanically driven. The second fuel pump usually has one in a pump room hinund forthcoming pump body, the frequency of Pump body rigidly to the speed of the internal combustion engine is coupled. Thus, despite the rigid coupling of Pump body to the speed of the internal combustion engine Flow rate of the second fuel pump can be controlled can, can between the first fuel pump and the second fuel pump a flow rate controlling Control valve can be provided during a pressure stroke the pump body a part of the fuel from the Pump room in the fuel connection between the first Flow back the fuel pump and the second fuel pump leaves. Thus within the fuel containing If there are no steam bubbles in the room, it is important that the connection from the first fuel pump into the pump room the second fuel pump monitoring, the flow rate controlling control valve during the suction stroke of second fuel pump the inflow of the fuel in does not throttle the pump room too much. That's why it is important that the control valve has a sufficiently large Has flow area.

Because the flow area must be relatively large, builds the control valve so far quite large and to Adjusting the flow area is a big and heavy electromagnet and a big, powerful spring required. Because of the required size of the flow area Until now it was not possible to use the control valve to build so that it switches fast enough, too at high frequency of the pump body of the second fuel pump a satisfactorily accurate control of the Pressure in the leading to the fuel valves To get pressure line.

Another disadvantage is that because of the previously required size of the control valve a relatively long Time passes until the flow area of the control valve is completely closed, so that in this transitional period a portion of the fuel from the pump room of the second Fuel pump in the fuel connection under relative high pressure flows back, which is an undesirable Energy loss and an undesirable heating of the fuel means.

Despite high expenditure it was not possible, that of the second fuel pump delivered amount of fuel even at high speed of the internal combustion engine sufficiently accurate to regulate and at the same time to ensure that in the second fuel pump no gas bubbles arise and the second fuel pump no excess fuel promotes energy loss and warming of the Fuel means.

Advantages of the invention

The fuel supply system according to the invention with the Characteristic features of claim 1 provides the Advantage that the control valve is relatively small overall can be dimensioned and still arises during the Flowing the fuel from the fuel connection in the pump chamber through the relatively large flow area a relatively small flow resistance. This in turn has the advantage that when the fuel flows into the Pump room the risk of the formation of a gas bubble in the Fuel despite using a relatively small control valve is greatly reduced.

Characterized in that the flow of the fuel through the opened control valve from the pump room back towards the leading to the first fuel pump fuel connection the flow area made relatively small is, one gets the advantage that only a relative small flow area must be controlled so that it with relatively little effort is possible, the control valve to be carried out so that the flow area very fast closed or can be opened.

By the measures listed in the dependent claims are advantageous developments and improvements the fuel supply system according to claim 1 possible.

By closing the flow area in dependence an operating condition of the internal combustion engine, the amount of fuel delivered by the second fuel pump in a very simple way and with little dissipation very much be precisely controlled or regulated. The invention running control valve can be particularly fast and closed or opened at the exact time.

Will the solenoid of the valve member adjusting Actuator still while the actuator of the actuator is in its unoperated rest position, d. H. some time before the actuator body its adjusting movement to execute, depending on a condition of the operating Internal combustion engine and / or in dependence of a pressure within the fuel supply system, in particular in Dependence of an attacking on the valve member Dynamic pressure and / or as a function of time, in particular depending on the instantaneous position of the pump body and / or depending on a pump speed adapted differently energized, then one obtains thereby the advantage that the solenoid just so much power builds up that the adjusting body still in its rest position remains, but then to the actuator body from his Rest position to adjust, only a minor Change of the current supply can be caused, which within can happen extremely short time, so that the actuator body and thus also actuated by the actuator valve member extremely quickly switched to the new intended position can be.

When you run the control valve so that by energizing of the electromagnet, the generated magnetic force the valve member adjusted to a closed position in which the flow area the control valve is closed, you get the Advantage that the solenoid of the control valve in total must be energized for a relatively short time, because the required Time span in which the flow area is open should, is usually longer than the period in which the Flow section should be closed.

If the control valve is designed so that when decreasing Energizing or switching off the energization of the electromagnet the counteracting the magnetic force of the electromagnet Spring displaces the valve member into a closed position, in which the flow area is closed, so one gets the advantage that even with a functional failure the electromagnet of the control valve, the second fuel pump the fuel from the fuel connection in the too can promote the fuel valves leading pressure line.

Is the control valve designed so that when flowing the Fuel from the fuel connection in the pump room lift off the valve member from the actuating body of the actuator can, then you get the advantage that while only the valve member, which has only a relatively small mass moves must be, which is characterized by rapid response of the valve member noticeable to pressure changes in an advantageous manner power. Another advantage is that the actuator body All in all, there is little way to go, and yet it is possible that the valve member has an overall longer Can travel adjustment path.

If the control valve is designed as a so-called seat valve, then can with relatively little displacement of the valve member advantageously a relatively large flow area controlled or opened and closed.

drawing

Selected, particularly advantageous embodiments of the Invention are shown in simplified form in the drawing and explained in more detail in the following description. Show it Figure 1 in symbolic form a preferred selected advantageous embodiment, Figure 2 is a detail of the embodiment and Figures 3 and 4 a Detail of another particularly advantageous executed Embodiment of the fuel supply system.

Description of the embodiments

The fuel supply system according to the invention for Metering of fuel for an internal combustion engine can at used different types of internal combustion engines become. As fuel is preferably a gasoline fuel, especially gasoline, used. The internal combustion engine is For example, a gasoline engine with external or internal Mixture formation and spark ignition, the engine with a reciprocating piston (reciprocating engine) or with a rotatably mounted piston (Wankel piston engine) be provided can. The ignition of the fuel-air mixture happens usually with a spark plug. The internal combustion engine is for example a hybrid engine. With this engine with Charge stratification becomes the fuel-air mixture in the combustion chamber Enriched in the area of the spark plug so far that a safe ignition is guaranteed, combustion in the Medium but takes place in a strongly lean mixture.

The gas change in the combustion chamber of the internal combustion engine can for example, after the four-stroke process or after Two-stroke procedure done. For controlling the gas exchange in the Combustion chamber of the internal combustion engine can in a known manner Gas exchange valves (intake valves and exhaust valves) provided be. The internal combustion engine can be designed in such a way that at least one fuel valve directly into the fuel the combustion chamber of the internal combustion engine injected. The control the performance of the internal combustion engine takes place depending on the operating mode by controlling the combustion chamber supplied Amount of fuel. But there is also an operating mode at which for the combustion of the fuel the combustion chamber supplied air is controlled by a throttle valve. Also on the position of the throttle, the of the Internal combustion engine to be delivered power controlled.

The internal combustion engine has, for example, a cylinder with a piston, or it can with multiple cylinders and be provided with a corresponding number of pistons. Preferably, one fuel valve per cylinder is provided.

To the extent of the description is not unnecessarily extensive to fail, the following is limited Description of the embodiments of a reciprocating engine with four cylinders as internal combustion engine, wherein the four fuel valves fuel, usually gasoline, Inject directly into the combustion chamber of the internal combustion engine. The ignition of the fuel in the combustion chamber takes place over a spark plug. Depending on the operating mode, the power the internal combustion engine via control of the injected Fuel quantity or via a restriction of the incoming Be controlled by air. At idle and lower part load there is a charge stratification with fuel enrichment in Area of the spark plug. The mixture is outside This area around the spark plug is very lean. At full load or upper part load is a homogeneous distribution between Fuel and air in the entire combustion chamber sought.

1 shows a fuel tank 2, a suction line 4, a first fuel pump 6, an electric motor 8, a filter 9, a fuel connection 10, a second fuel pump 12, a pressure line 14, four fuel valves 16, a power supply unit 18 and an electrical or electronic control device 20. The fuel valves 16 are often referred to in the art as injectors or injectors.

The first fuel pump 6 has a pressure side 6h and a suction side 6n. The second fuel pump 12 has a High pressure side 12h and a low pressure side 12n. The fuel connection 10 leads from the pressure side 6h of the first Fuel pump 6 to the low pressure side 12n of the second Fuel pump 12. From the fuel connection 10 branches a fuel line 22 from. Via the fuel line 22 can fuel from the fuel 10 directly in the fuel tank 2 are returned. In the fuel line 22 is a pressure regulating valve or Pressure control valve 26 is provided. The pressure control valve 26 works as a pressure relief valve or as a Differential pressure valve; It ensures that in the fuel connection 10 a largely constant feed pressure Regardless of how much fuel from the second fuel pump 12 from the fuel connection 10th is removed. The pressure control valve 26 regulates the pressure for example, to 3 bar, which corresponds to 300 kPa.

The first fuel pump 6 is driven by the electric motor 8. The first fuel pump 6, the electric motor 8 and the pressure control valve 26 are in the range of Fuel tank 2. These parts are preferably arranged outside the fuel tank 2 or located inside the fuel tank 2, what symbolically represented by a dot-dash line is.

Via a mechanical transmission means 12m is the second Fuel pump 12 mechanically with a not shown Output shaft of the internal combustion engine coupled. Because the second fuel pump 12 mechanically rigidly to the output shaft the internal combustion engine is coupled, the works second fuel pump 12 purely proportional to the speed of the Output shaft of the internal combustion engine. The speed of the Output shaft is, depending on the current operating condition the internal combustion engine, very different. at the output shaft is for example a Camshaft of the internal combustion engine.

The second fuel pump 12 has a pump room 28. In the fuel connection 10, on the low pressure side 12n the second fuel pump 12 is located on the input side in front of the pump chamber 28, a control valve 30. The control valve 30 essentially serves to control the second Fuel pump 12 to be pumped amount of fuel, why the control valve 30 as a quantity control valve can be designated. This will be even closer explained. In the pressure line 14, on the high pressure side 12h of the second fuel pump 12, is an output side Check valve 32 is provided.

The second fuel pump 12 is located within a with dash-dotted lines symbolically indicated housing 12g. Also, the check valve 32 may be within of the housing 12g are located. The control valve 30 has a Valve body 30g. The valve housing 30g is attached to the housing Flanged 12g or integrated into the housing 12g. The Control valve 30 can also be installed directly in the housing 12g be.

The from the second fuel pump 12 to the fuel valves 16 leading pressure line 14 can simplify be divided into a line section 42, a Storage space 44 and in distribution lines 46. The fuel valves 16 are each a distribution line 46 to the Memory space 44 connected. A pressure sensor 48 is connected to the Memory space 44 connected and senses the respective Pressure of the fuel in the pressure line 14. Accordingly This pressure is the pressure sensor 48, an electrical signal to the control device 20.

Is the pressure of the fuel in the pressure line 14 too high, then fuel from the pressure line 14 via a Return line 52 passed into the fuel connection 10. In the return line 52, there is a pressure relief valve 53. The pressure relief valve 53 ensures that the pressure of the fuel in the pressure line 14 is not a certain maximum value even if, as a result of any Defect the second fuel pump 12 undesirably much Fuel in the pressure line 14 pumps.

The fuel supply system further includes a sensor 54 or more sensors 54 and an accelerator pedal sensor 56. The sensors 54, 56 sense the operating condition, below the internal combustion engine is working. The operating condition for the internal combustion engine may consist of several single operating conditions put together. The single operating conditions are for example: temperature and / or pressure of the fuel in the fuel connection 10, temperature and / or pressure of the fuel in the pressure line 14, air temperature, Cooling water temperature, oil temperature, engine speed the internal combustion engine or speed of the output shaft the internal combustion engine, composition of the exhaust gas the internal combustion engine, injection time of the fuel valves 16, etc. The accelerator pedal sensor 56 is located in the region of Accelerator pedal and detects, as another single operating condition, the position of the accelerator pedal and thus the desired by the driver Speed.

The electric motor 8, the fuel valves 16, the pressure sensor 48 and the sensors 54, 56 are via electrical Lines 58 connected to the controller 20. The electrical line 58 between the fuel valves 16 and the controller 20 is configured so that the Control device 20 of each of the fuel valves 16 can control separately. For better distinction over the other non-electrical lines are the electrical lines 58 shown in phantom.

The first fuel pump 6 is For example, a robust, easy to produce Positive displacement pump, which is essentially a specific Constant amount of fuel promotes.

The pressure of the fuel in the fuel connection 10 on the pressure side 6h of the first fuel pump 6 becomes below referred to as feed pressure. In the proposed Fuel supply system determines the pressure control valve 26 the feed pressure in the fuel connection 10th

The second fuel pump 12 delivers the fuel from the Fuel connection 10, through the control valve 30 in the Pump chamber 28 and from the pump chamber 28 through the output-side check valve 32 in the pressure line 14th

The pressure in the pressure line 14 may during the normal Operating state, for example, be around 100 bar, which 10 MPa corresponds. That's why it's important to make sure that the second fuel pump 12 exactly the instantaneous required amount of fuel in the pressure line 14 pumps, so that no fuel from the pressure line 14 in the low pressure area of the fuel supply system must be returned, which is very undesirable, unnecessary Would mean dissipation.

The control valve 30 shown symbolically in FIG is in a first valve position 30.1, in a second Valve position 30.2 and in a third valve position 30.3 switchable. The symbolic valve positions 30.1, 30.2, 30.3 are just for the sake of clarity shown because of different sizes.

The control valve 30 has an actuator 60. The actuator 60 essentially comprises an electromagnet 62 and one of the magnetic force of the electromagnet 62 counteracting Spring 64. By energizing or non-energizing the Electromagnet 62, the control valve 30 in the first Valve position 30.1 or in the second valve position 30.2 connected. The control valve 30 has a valve member 66 (Figure 2). The valve member 66 is separated from that by the control valve 30 flowing therethrough of the fuel against the force of a contact spring 68 actuated. At flow of Fuel from the fuel connection 10 in the pump room 28 of the second fuel pump 12, so if the pressure in the fuel connection 10 is greater than the pressure in the Pump chamber 28, the valve member 66 (Fig. 2) of the Flow of the fuel against the force of the application spring 68 adjusted so that the control valve 30 in the in the Figure 1 symbolically shown third valve position 30.3 located. Is the pressure in the pump chamber 28 greater than in the Fuel connection 10, then the fuel flows from Pump chamber 28 back into the fuel connection 10 and the Valve member 66 is adjusted so that the control valve 30 in the symbolically shown in Figure 1 second Valve position 30.2 is located. The contact spring 68 also provides in that the valve member 66 (Figure 2) is actuated by the actuator 60 can follow adjustment movement and the Control valve 30 enter the first valve position 30.1 can. To show graphically that the control valve 30th between the two valve positions 30.2 and 30.3 pressure-dependent is switchable, are symbolic in the figure 1 two control lines or control spaces 10a and 28a located.

In the first valve position 30.1 the connection or a flow area 74 between the fuel connection 10 and the pump room 28 locked. In the second Valve position 30.2, the control valve 30 has the flow area 74 just slightly open, and the fuel can with some throttling from the pump room 28 back in the fuel connection 10 flow. In the third valve position 30.3, the control valve 30 has the flow area 74 wide open, and the fuel can be largely unthrottled from the fuel connection 10 in the pump room 28 flow in.

The second fuel pump 12 is constructed so that the Pump chamber 28 alternately enlarged and reduced, while the internal combustion engine via the transmission means 12m, the second fuel pump 12 drives. The pump room 28 increases or decreases, for example, by a pump body 72 (FIG. 2) mounted in the housing 12g from the internal combustion engine via the mechanical Transfer means 12m to axially reciprocating Movement is driven. During a suction stroke the second fuel pump 12, d. H. when the pump body 72 down (relative to Fig. 2) moves, increases the pump chamber 28. During a pressure stroke, i. H. if the Pump body 72 pressed upward (relative to FIG. 2) is, then the pump chamber 28 is reduced.

During a suction stroke, while the pump room 28 increases, the electromagnet 62 is not energized and the from the fuel connection 10 in the pump chamber 28th inflowing fuel displaces the valve member 66 (Fig. 2), so that the control valve 30 in the third Valve position 30.3 is located, whereby the flow area 74 of the control valve 30 is wide open and the Fuel largely unthrottled from the fuel connection 10 can flow into the pump chamber 28. At average Operating condition of the internal combustion engine is in the subsequent pressure stroke while the pump chamber 28 reduced, the electromagnet 62 initially energized, and the control valve 30 is in its second valve position 30.2. As long as the control valve 30 in the Valve position is 30.2, pushes the second fuel pump 12 the fuel from the pump chamber 28 through the Control valve 30 back into the fuel connection 10th Depending on the current operating condition of the Internal combustion engine, in particular depending on which Pressure of the pressure sensor 48 sensed in the pressure line 14 and depending on how much fuel the fuel valves 16 instantly into the combustion chambers of the internal combustion engine to squirt, calculates the controller 20 the time at which the flow area 74 of the Control valve 30 is to be closed. To close the Durchflußquerschnitts 74, the electromagnet 62 is energized, and the control valve 30 is in its first valve position 30.1 switched. Because the control valve 30 before in has found his second valve position 30.2, in the Flow section 74 is not open to the maximum, is the Way, the valve member 66 (Fig. 2) for closing the Durchflußquerschnitts 74 must travel, only relatively short, so that the closing of the flow area 74 very can happen quickly. This is necessary to a very accurate regulation of the pressure of the fuel in the To be able to reach pressure line 14. Characterized in that the flow area 74 closed very quickly and then can be opened again very quickly, it is possible also a very fast second fuel pump 12 to use, in which the pump body 72 very fast hinund is moved, so that the pump chamber 28 very quickly increased or decreased. Because at fast operating times of the pump body 72 (FIG. 2) Suction stroke and the pressure stroke are very short, it is important that the control valve 30 quickly and accurately the flow area 74 opens or closes. By choosing the time, to the during a pressure stroke, the control valve 30 of the second valve position 30.2 in the first valve position 30.1 is the amount of fuel that can be switched second fuel pump per pressure stroke from the fuel connection 10 in the pressure line 14 promotes to be determined.

FIG. 2 shows by way of example a section of the first exemplary embodiment. The parts not shown in Figure 2 correspond to those shown in the remaining figures. FIG. 2 essentially shows a longitudinal section through the control valve 30, which is in the unactuated switch position 30.2.

In all figures are the same or equivalent parts with provided the same reference numerals. Unless otherwise stated mentioned or shown in the drawing, applies the one mentioned and represented by one of the figures also in the other embodiments. As far as the Unless otherwise stated in the explanation, the details are The various embodiments combined with each other.

The actuator 60 includes in addition to the electromagnet 62 and the spring 64 is a control body 76. The actuator 76 is composed of an armature 76a and one with the anchor 76a fixedly connected plunger 76b. When not energized Electromagnet 62 pushes the spring 64, the actuating body 76th down (relative to FIG. 2) until the armature 76a abuts a lower, provided on the valve housing 30g stop disc 78u comes to the plant. With sufficiently strong Energization of the electromagnet 62 is the actuator 76th up (FIG. 2) against the force of the spring 64, until the armature 76a at an upper, on the valve housing 30g provided stop disc 78o is applied.

On the valve housing 30g, a valve seat 80 is provided. at not energized electromagnet 62 is the between the Valve seat 80 and the valve member 66 extending flow area 74 as far as it is in the figure 2 is shown. FIG. 2 shows the control valve 30 in FIG the second valve position 30.2. In the second valve position 30.2 is the distance between the valve seat 80 and the valve member 66 is relatively low, so that for switching to the first valve position 30.1 (Fig. 1) of the actuating body 76th only very slightly upwards (relative to FIG. 2) moves must be until the valve member 66 to close the flow area 74 comes to rest on the valve seat 80. As a result, the flow area 74 can be very fast getting closed. Supported is the clasp of the Throughflow 74 through the during the pressure stroke in Pump chamber 28 increasing pressure. As FIG. 2 shows, the pressure acts in the control room 10 a, in which the im essentially the same feed pressure as in the fuel connection 10 prevails, on the valve member 66 down in Opening direction, and the pressure in the control chamber 28 a, in the the substantially same pressure as in the pump chamber 28th prevails acts on the valve member 66 upwards in the closing direction.

During a suction stroke, the pump body 72 moves below (with reference to FIG. 2). This reduces the pressure of the Fuel in the pump chamber 28 below the feed pressure of Fuel in the fuel connection 10. This pressure difference acts on the valve member 66 down (Fig. 2) against the force of the application spring 68. The force of Apply spring 68 is quite small, so that already a small pressure difference between the fuel connection 10 and the pump chamber 28, the valve member 66 hydraulically after below (Fig. 2) presses. This ensures that the Pressure in the pump chamber 28 does not sink too far, so that no unwanted gas bubbles in the pump chamber 28 may arise. If the valve member 66 is pressed down hydraulically (FIG. 2), then raises the valve member 66 of the actuator body 76th of the actuator 60 from. By taking off is achieved that of the pressure difference between the pump chamber 28th and the fuel connection 10 hydraulically acted upon Valve member 66 in total only a small mass to be moved has, which gives the advantage that already a small Pressure difference, the valve member 66 dynamically very fast adjusted in the direction you want. With others Words, even a small pressure difference displaces that Valve member 66 against the force of the application spring 68 down (Fig. 2) and upwards (Fig. 2), to the valve member 66 at the plunger 76b of the actuating body 76 or on the valve seat 80th comes to the plant. The valve member 66 can from the valve seat 80th or from the actuator 76 so far lift until the valve member 66 at a provided on the valve housing 30g valve member stop 82 comes to the plant.

In the embodiment shown in Figures 1 and 2 the control valve 30 is energized by energizing the Electromagnet 62 in the first valve position 30.1 (FIG. 1) adjusted, in which the flow area 74 is closed is. In contrast, in the following is based on the Figures 3 and 4 explained embodiment during energizing of the electromagnet 62 of the flow area 74th open. In comparison to that in Figures 1 and 2 illustrated embodiment are in the in the Figures 3 and 4 shown embodiment, the directions the magnetic force of the electromagnet 62 and the spring force the spring 64 of the actuator 60 reversed.

Figures 3 and 4 show another preferred, particularly advantageous embodiment. FIG. 3 shows the exemplary embodiment when the electromagnet 62 is not energized, so that the control valve 30 is in the first valve position 30.1, in which the flow area 74 is closed. FIG. 4 shows the second exemplary embodiment when the electromagnet 62 is fully energized, whereby the control valve 30 is in the second valve position 30.2.

When the pump chamber 28 in the in Figs. 3 and 4 illustrated embodiment during a suction stroke increases, then the pressure in the pump chamber 28 decreases, and the Fuel flows from the fuel connection 10 through the Flow section 74 in the pump chamber 28, wherein the fuel flowing through the valve member 66 from the valve seat 80 takes off. In this case, the flow area 74 can be full open so that the fuel with very low pressure loss can flow into the pump chamber 28.

During the suction stroke, it is not absolutely necessary that the electromagnet 62 is energized. It will, however proposed, at least towards the end of the suction stroke, at the latest just before the beginning of the compression stroke, the electromagnet 62 to energize, so that the actuator body 76 down in the in 4 valve position 30.2 shown is adjusted. This ensures that at the beginning of the print stroke of Flow section 74 is opened, so that the not in the pressure line 14 needed fuel in the fuel connection 10 can flow back. Because at the beginning of the Druckhubs the valve member 66 rests against the actuating body 76 and between the valve seat 80 and the valve member 66 only one small distance, the valve member 66 must for Close the flow area 74 only a short way cover so that closing the flow area 74 can happen very quickly. During the print stroke can the flow area 74 will be much smaller than during the suction stroke.

Based on calculations, the controller determines 20 the time at which during the print stroke the Energization of the electromagnet 62 is turned off, thereby the adjusting body 76 upwards (with reference to FIGS. 3 and 4) is moved, and the valve member 66 closes by conditioning on the valve seat 80, the flow area 74. By Switching off the energization of the electromagnet 62 of the actuator 60, the control valve 30 during a pressure stroke from the second valve position 30.2 shown in FIG in the illustrated in Figure 3 first valve position 30.1 be switched very quickly. After switching to the first valve position 30.1 pushes the pump body 72 the Fuel from the pump chamber 28 through the output side Check valve 32 in the pressure line 14. By variation the time of switching of the control valve 30, the respectively required amount of fuel with high dosing accuracy be pumped into the pressure line 14.

The fuel supply system has a following Emergency function described: If in the in the figures 3 and 4 illustrated embodiment of the electromagnet 62nd should fail as a result of a defect or his Power supply is interrupted, then it is Valve member 66 during the entire pressure stroke in the in Figure 3 shown position in which the flow area 74 is closed, so that the whole of the Pump chamber 28 during the pressure stroke displaced amount of fuel through the outlet-side check valve 32 in the pressure line 14 is pumped. During the suction stroke can the valve member 66 even in the event of failure of the electromagnet 62, lift off from valve seat 80 as previously described. at Failure of the solenoid 62 of the actuator 60, the pump the second fuel pump 12 anyway, but without the possibility of accurate metering of the pressure line 14 pumped fuel quantity. The of the fuel valves 16 not needed and therefore not removed excess subset of fuel leads doing so to a pressure increase in the pressure line 14 until the Relief valve 53 (Fig. 1) responds and not required fuel from the pressure line 14 through the Return line 52 back into the fuel connection 10 or, in a modified version, back into the fuel tank 2 is performed. In case of failure of the electromagnet 62, the internal combustion engine with an emergency function continue working. Once the controller 20 determines that the pressure sensor 48 senses a pressure that is higher than the pressure due to activation the control valve 30 would have to recognize the recognizes Control device 20 that the emergency function occurred is. Because during the emergency function, an exact dosage of in the pressure line 14 funded fuel quantity not is possible, it is proposed, the control device 20 in such a way that a corresponding error message to Display is brought.

Below a note, as for the switching of the Control valve 30 required switching period in addition can be significantly shortened: So that in the in the Figures 1 and 2 illustrated embodiment in all occurring operating conditions, d. H. at all occurring pressures in the fuel connection 10 and in Pump chamber 28 and at all flow rates of the Fuel through the flow area 74, the spring 64th the valve member 66 in the second shown in the figure 2 The valve position 30.2 can be actuated and held there, the must Spring 64 correspondingly strong enough dimensioned be. But there are operating conditions in which to hold of the valve member 66 in the second valve position 30.2 not the full force of the spring 64 is needed. In order to subsequently, when the valve member 66 the flow area 74 to close, the switching even faster can happen, it is suggested that as long as that Valve member 66 still in the second valve position 30.2 should remain, the solenoid 62 is energized so far, that the force of the spring 64 minus the magnetic force of Solenoid 62 is just enough to the valve member 66th to be held securely in the second valve position 30.2. is then the time came to which the flow area 74 is closed, it is sufficient a relatively small additional energization of the electromagnet 62. This slight additional energization of the electromagnet 62 can be done in a much shorter time than if the Electromagnet 62, starting from the completely de-energized State should be energized.

A significant influence on the required force for Holding the valve member 66 in the second valve position 30.2 is the pressure of the fuel in the pump chamber 28 at Pushing back the fuel from the pump chamber 28 in the Fuel connection 10. This is in the pump room 28 essentially to a back pressure. The dynamic pressure is mainly determined by the flow velocity, with the fuel from the pump chamber 28 is displaced. The Flow rate depends on the speed of the upwards moving pump body 72 from. The speed the pump body 72 is determined by the pump speed, with which the fuel pump 12 is driven by the camshaft becomes. It is therefore proposed, the electromagnet 62 preferably in response to the valve member To energize 66 attacking dynamic pressure, then only spend even a little additional power to switch to have to. Because the dynamic pressure of the speed of the upwardly moving pump body 72 depends, in turn the pump speed corresponds, it is proposed that Electromagnet 62 in dependence on the pump speed energize.

If at the beginning of the pressure stroke, the control valve 30 in the second valve position 30.2 is and the flow area 74 is open, then is at low pump speed the valve member 66 acting in the closing direction acting dynamic pressure lower than at high pump speed. To hold the valve member 66 in the second Valve position 30.2 must therefore the force of the actuator 60th in the opening direction at high pump speed essential be larger than at low pump speed. At all Pump speeds to get as short a closing time as possible, is proposed some time before the intended Switching from the second valve position 30.2 (Fig. 2) in the first valve position 30.1, the electromagnet 62 already in advance to energize something and so on stronger, the smaller the pump speed is.

Also in the embodiment shown in Figures 3 and 4 can be used for switching the control valve 30 required switching period in addition be significantly shortened. Here, the solenoid 62 must of the actuator 60 so strong enough dimensioned be that if necessary under all operating conditions of Electromagnet 62, the valve member 66 in the in the Figure 4 reproduced second valve position 30.2 can keep in the flow area 74 is opened. The required magnetic force of the electromagnet 62 for holding the valve member 66 is, however, in the majority of Operating conditions lower. It is suggested that at the operating conditions where a lower magnetic force of the electromagnet 62 is sufficient to the valve member 66 in the second valve position 30.2 to keep the Electromagnet 62 is energized correspondingly lower. Should then then the flow area 74 completely closed, the magnetic force of the electromagnet falls 62 down to zero much faster, and the spring 64 can the adjusting body 76 much faster upwards (Fig. 4), as if in the second valve position 30.2 the electromagnet 62 would be maximally energized.

At all pump speeds, the shortest possible closing time It is suggested to get some time before intended switching from the second valve position 30.2 (FIG. 4) into the first valve position 30.1 (FIG. 3) Electromagnet 62 already in advance a little less strong energize and that less, the smaller the pump speed is.

Because the voltage of the electrical power unit 18 (Figure 1) is usually limited, it takes from the beginning the switching on of the electromagnet 62 a certain time, until the solenoid 62 with its full maximum magnetic force can act on the actuator 76. In the in the Figures 3 and 4 illustrated embodiment is in Turning off the magnetic force of the electromagnet 62 of the flow area 74 closed, in particular the Closing the flow area 74 particularly fast, within a short time, should happen. Because it is possible is, the controller 20 in such a way that the Turning off the magnetic force happens faster than that Switching on the magnetic force, results in the in the Figures 3 and 4 illustrated embodiment advantageously a particularly short closing time when closing the flow area 74, because here to close the Durchflußquerschnitts 74, the magnetic force of the electromagnet 62 must be turned off. Therefore, in the second Embodiment of the second fuel pump 12th Promoted fuel quantity controlled very precisely become.

Claims (15)

1. Fuel supply system for delivering fuel for an internal combustion engine, having a fuel reservoir container, a first fuel pump (6), a second fuel pump (12) and having a pressure line (14) to which at least one fuel valve (16), via which the fuel can pass at least indirectly into a combustion chamber of the internal combustion engine, is connected, the first fuel pump (6) conveying the fuel from the fuel reservoir container (2) into a fuel connection (10), and the second fuel pump (12) having a pump space (28) and substantially conveying the fuel from the fuel connection (10) through a control valve (30) with a variable flow passage (74) into the pump space (28) and from the pump space (28) into the pressure line (14), characterized in that the control valve (30) comprises a valve element (66) which influences the flow passage (74), the valve element (66) influencing the flow passage (74) in such a way that the flow passage (74) is larger when the fuel is flowing from the fuel connection (10) into the pump space (28) than when the fuel is flowing from the pump space (28) into the fuel connection (10).
2. Fuel supply system according to Claim 1, characterized in that the valve element (66) can close the flow passage (74) as a function of an operating condition of the internal combustion engine.
3. Fuel supply system according to one of the preceding claims, characterized in that the valve element (66) can be displaced by a driveable actuating body (76) of an actuating drive (60), the actuating drive (60) comprising, in order to displace the actuating body (66), an electromagnet (62) and a spring (64) counteracting a magnetic force of the electromagnet (62).
4. Fuel supply system according to Claim 3, characterized in that the actuating body (76) has an unactivated rest position, current being supplied to the electromagnet (62) as a function of an operating condition of the internal combustion engine while the actuating body (76) remains in the unactivated rest position.
5. Fuel supply system according to Claim 3, characterized in that the actuating body (76) has an unactivated rest position, in which case, while the actuating body (76) remains in the unactivated rest position, current is supplied to the electromagnet (62) as a function of a back pressure acting on the valve element (66).
6. Fuel supply system according to Claim 3, characterized in that the actuating body (76) has an activated position, in which case, while the actuating body (76) remains in the activated position, current is supplied to the electromagnet (62) as a function of a back pressure acting on the valve element (66).
7. Fuel supply system according to Claim 3, characterized in that the actuating body (76) has an unactivated rest position, current being supplied to the electromagnet (62) differently as a function of time while the actuating body (76) remains in the unactivated rest position.
8. Fuel supply system according to one of Claims 3 to 7, characterized in that the magnetic force produced when current is supplied to the electromagnet (62) ensures a closed position, closing the flow passage (74), of the valve element (66) (Figure 2).
9. Fuel supply system according to one of Claims 3 to 7, characterized in that a closing force, becoming effective when decreasing current is supplied to the electromagnet (62), of the counteracting spring (64) ensures a closed position, closing the flow passage, of the valve element (66) (Figures 3 and 4).
10. Fuel supply system according to one of Claims 3 to 9, characterized in that the valve element (66) lifts off from the actuating body (76) when the fuel flows from the fuel connection (10) into the pump space (28).
11. Fuel supply system according to one of Claims 3 to 10, characterized in that a holding spring (68) is provided which holds the valve element (66) against the driveable actuating body (76) of the actuating drive (60).
12. Fuel supply system according to Claims 10 and 11, characterized in that the valve element (66) lifts off from the actuating body (76) counter to a force of the guiding spring (68).
13. Fuel supply system according to Claim 10 or 11, characterized in that a spacing between a valve seat (80) of the control valve (30) and the valve element (66) is increased when the valve element (66) lifts off from the actuating body (76).
14. Fuel supply system according to one of the preceding claims, characterized in that the second fuel pump has a driveable pump body (72), the pump body (72) alternately enlarging and reducing the pump space (28) as a result of the said pump body (72) being driven.
15. Fuel supply system according to one of the preceding claims, characterized in that the control valve (30) is a seat valve.

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