EP1278950B1 - Method for operating a fuel supply system for an internal combustion engine, especially in a motor vehicle - Google Patents

Abstract

Disclosed is a fuel supply system (1) for an internal combustion engine, especially in a motor vehicle. In said fuel supply system (1), fuel can be pumped by a pump (6, 10) into a pressure accumulator (2). The pressure inside the pressure accumulator (2) can be measured and the pressure in said pressure accumulator (2) can be modified by controlling a pressure control valve (4). The pressure control valve (4) can be fully opened by means of a control device (16) and the pressure measured inside the pressure accumulator (2) can be compared to the expected pressure using said control device (16).

Description

State of the art

The invention relates to a method for operating a Fuel supply system for an internal combustion engine in particular of a motor vehicle, wherein the fuel of a pump is pumped into a pressure accumulator, in which the pressure in the pressure accumulator is measured, and in the the pressure in the accumulator by the control of a Pressure control valve is changeable. Furthermore it concerns the invention a corresponding Fuel supply system for an internal combustion engine and a control device for such Fuel supply system.

To an internal combustion engine, for example one Motor vehicles are becoming increasingly demanding in the With regard to a reduction of fuel consumption and the generated exhaust gases at a simultaneously desired increased performance. For this purpose are modern Internal combustion engines with a fuel supply system provided in which the supply of fuel in the Combustion chamber of the internal combustion engine electronically, in particular with a computerized control unit, controlled and / or is regulated. It is possible to use the fuel in one Air intake pipe of the internal combustion engine or directly into the Inject combustion chamber of the internal combustion engine.

In particular, in the latter type, the so-called Direct injection, it is necessary that the fuel is injected under pressure into the combustion chamber. To this Purpose is a pressure accumulator provided in the Fuel pumped by a pump and under a high pressure is set. From there, the fuel will be via injection valves into the combustion chambers of the Internal combustion engine injected.

Due in part to the high pressure, it is possible that Components of the fuel supply system e.g. due to aging change. So it is possible that that Pressure control valve, with which the pressure in the pressure accumulator controlled and / or regulated, slowly his Functionality changed. It is also possible that the pressure control valve due to contamination abruptly fails. Such changes in function of the pressure control valve may dropouts or a other faulty running of the internal combustion engine for Episode.

An error of a pressure control valve connected to a COMMON -RAIL accumulator of an injection system, is after the State of the art (DE 196 04 552 A, BOSCH GMBH ROBERT, Claims) recognized when at fully open pressure control valve the measured pressure drop is too small.

Purpose and advantages of the invention

The object of the invention is in the Fuel supply system for a Internal combustion engine one slowly occurring error of the pressure control valve quickly and sure to recognize. This task will solved with the features of the independent claims.

If the pressure control valve is fully open, so has This entails that at the pressure control valve a back pressure arises. This dynamic pressure can be intact Pressure control valve to be determined in advance. The dynamic pressure is in particular parameters of the pressure control valve dependent, such as the flow cross-section thereof. By measuring the actual pressure in the accumulator after the full opening of the Pressure control valve is ultimately the currently available Back pressure measured at the pressure control valve. This measured back pressure is then with the expected back pressure compared and then from the comparison can on the Functioning of the pressure control valve closed become.

The inventive method can quickly and without a substantial additional effort. Of further can be reliably detected by the method, whether the pressure control valve is intact or not. The The inventive method can in the operation of the Internal combustion engine, but also as part of a review the same e.g. be done in a workshop.

It is particularly advantageous if the pressure in the Accumulator only after a waiting period after opening the Pressure control valve is measured. This will ensure that the back pressure on the pressure control valve completely has built up.

In advantageous developments of the invention, the expected pressure depending on parameters of a intact pressure control valve and / or depending on determined current operating variables of the internal combustion engine.

It is then recognized the pressure control valve as dirty, when the measured pressure is greater than the expected one Print.

In an advantageous embodiment of the invention is the internal combustion engine in the push mode or in idle mode. These are operating states of the Internal combustion engine in which the inventive Procedure is particularly good.

It is also advantageous if the temperature and / or the speed of the internal combustion engine in one permissible range is located. This is the reliability the method according to the invention further improved.

Embodiments of the invention

FIG. 1

shows a schematic representation of a Embodiment of an inventive Fuel supply system, and

FIG. 2

shows a schematic block diagram of a Embodiment of an inventive Method of operating the Fuel supply system of Figure 1.

FIG. 1 shows a fuel supply system 1 shown for use in a Internal combustion engine of a motor vehicle is provided. at the fuel supply system 1 is a So-called common rail system, in particular in a Internal combustion engine with direct injection for use comes. Such common rail systems are of gasoline; as Also known from diesel internal combustion engines.

The fuel supply system 1 has a pressure accumulator 2, which with a pressure sensor 3 and a Pressure control valve 4 is provided. The accumulator 2 is via a pressure line 5 with a high pressure pump. 6 connected. The high pressure pump 6 is via a pressure line 8 connected to the pressure control valve 4. Over a Pressure line 9 and a filter is the pressure control valve. 4 and thus also the high pressure pump 6 with a preferably electric fuel pump 10 connected to it is suitable for fuel from a fuel tank 11th to suck.

The fuel supply system 2 has four Injection valves 13, which via pressure lines 14 with the Pressure accumulator 2 are connected. The injection valves 13 are capable of delivering fuel into appropriate combustion chambers to inject the internal combustion engine.

By means of a signal line 15, the pressure sensor 3 with a control unit 16 connected to the one further Plurality of signal lines other than input lines are connected. By means of a signal line 17 is the Fuel pump 10 and a signal line 18 is the Pressure control valve 4 connected to the control unit 16. Of Further, the injection valves 13 by means Signal lines 19 connected to the control unit 16.

The fuel is from the fuel pump 10 from the Fuel tank 11 pumped to the high-pressure pump 6. With Help the high-pressure pump 6 is in the pressure accumulator 2 a Generates pressure, which is measured by the pressure sensor 3 and by a corresponding actuation of the pressure control valve 4 can be set to a desired value. about the injectors 13 will then be the fuel in the Combustion chamber of the internal combustion engine injected.

For the design of the injected into the combustion chamber Fuel quantity or fuel mass is among others Pressure in the pressure accumulator 2 essential. The bigger the Pressure in the pressure accumulator 2 is, the more fuel is in the combustion chamber during the same injection time injected. This pressure in the pressure accumulator 2 can from be set and adjusted the control unit 16.

For this purpose, the control unit 16 controls the pressure control valve. 4 in its closed state, so that the high pressure pump 6 and the fuel pump 10 one more and more generate increasing pressure in the pressure accumulator 2. Conversely, the controller 16 controls the pressure control valve 4 in its open state, so that the fuel off the pressure accumulator 2 flows again and the pressure in the accumulator 2 again reduced.

When fully opened, a dynamic pressure builds up the pressure control valve 4. This dynamic pressure is of the free flow cross-section of the pressure control valve 4 and depending on the amount of fuel flowing through. The The latter amount of fuel is again among other things depending on the speed of the internal combustion engine, the amount of the pumped fuel and the amount of in the Internal combustion engine of injected fuel.

After a longer period of operation of the pressure control valve. 4 it is possible that the flow cross-section of Pressure control valve 4 due to contamination or other deposits slowly narrowed. This leads to a creeping change of the of the pressure control valve. 4 influenced pressure in the pressure accumulator 2. In particular arises at a smaller flow cross section of the Pressure control valve 4 in the pressure accumulator 2 a larger Pressure as this should be the case. In extreme cases performs a complete transfer of the flow cross-section the pressure control valve 4 to its inoperability and thus failure of the fuel supply system. 1

With the method of Figure 2 is a creeping Pollution of the pressure control valve 4 detected. The The method of Figure 2 is the control unit 16 carried out.

In a block 21 is checked by the controller 16, whether the temperature of the internal combustion engine in one permissible range is located. This is required with it the method of Figure 2 are performed reliably can. If the temperature is not within the permissible range Range, the method of Figure 2 is aborted and restarted at a later date.

Is the temperature of the internal combustion engine in the permissible range, then in a subsequent block 22 checks whether the internal combustion engine is in the state of Thrust shutdown is located. In this state, the Internal combustion engine driven "from the outside". As an an example can be specified a downhill of a motor vehicle in which the driver neither the accelerator pedal, nor the Clutch pedal operated so that the motor vehicle with coupled gear, but without drive the mountain rolls down. In this state, the Internal combustion engine rolling downhill Motor vehicle "pushed". The condition is therefore too referred to as pushing operation (or overrun operation).

Is the internal combustion engine not in the Pushing operation, the method of FIG. 2 becomes canceled and repeated at a later date. However, is the internal combustion engine in Shift operation, so in a block 23 is the Pressure control valve 4 (DSV) completely from the control unit 16 open.

In a block 24 of the control unit 16 is a Waiting time waited until a back pressure on the Pressure control valve 4 has built. This waiting time is from the pressure control valve 4 dependent and can be determined in advance and stored in the controller 16.

After the waiting time is in a block 25 of the Pressure sensor 3, the pressure in the pressure accumulator 2 measured. This measurement is caused by the controller 16 and carried out. Due to the completely open Pressure control valve 4 is this measured Pressure around the back pressure on the pressure control valve. 4

In a subsequent block 26, the control unit 16 calculated a reference value for the dynamic pressure. In which Comparison value is an expected pressure, which would have to adjust with intact pressure control valve 4. The comparison value depends on the current one Operating state of the internal combustion engine, ie of the current operating variables thereof, such as e.g. their Speed, engine temperature, and the like. Furthermore is the comparison value depends on parameters of the Pressure control valve 4, which in a characteristic or a Map are stored in the controller 16. The mentioned parameters refer to an intact Pressure control valve 4 and can in particular in advance on a new pressure control valve 4 is determined and then in the Control unit 16 are stored.

In a subsequent block 27 is again from the Control unit 16 checks if the internal combustion engine is still in the state of fuel cutoff. Is this no longer the case, then the method of Figure 2 canceled and repeated at a later date.

Is the internal combustion engine still in the Shift operation, so is the control unit 16 in a Block 28 is the measured back pressure with the comparison value (MaxValue) compared. Is the measured dynamic pressure smaller? as the comparison value, it is from the control unit 16 in a block 29 on an intact pressure control valve. 4 closed.

If, on the other hand, the measured back pressure is greater than that calculated comparison value, so is the controller 16 in a block 30 on a pollution of the Flow cross-section of the pressure control valve 4 is closed.

In the method described above, it is possible that instead of the shift operation, an idle operation of Internal combustion engine for druchführung the process is selected. It is also possible that in addition to the condition that the temperature of the Internal combustion engine are within a permissible range must, as further requirement for the execution of the Process of Figure 2, the speed of the Internal combustion engine are within a permissible range got to.

The method described above can during the Operation of the internal combustion engine are performed. It is also possible that procedures in the workshop with the help of an appropriate test device to let.

The mentioned parameters of the intact pressure control valve 4 can be general for a particular Internal combustion engine type, but also individually for each Internal combustion engine can be determined and stored. at an exchange of the pressure control valve 4 can new Parameter determined and read into the control unit 16 become.

Claims (10)

1. Method for operating a fuel supply system (1) for an internal combustion engine, in particular in a motor vehicle, in which fuel is pumped by a pump (6, 10) into a pressurized store (2), in which the pressure (prist) in the pressurized store (2) is measured, and in which the pressure (prist) in the pressurized store (2) can be changed by actuation of a pressure control valve (4), characterized in that the pressure control valve (4) is completely opened, in that the pressure measured is the dynamic pressure at the pressure control valve (4), on account of the pressure control valve (4) being completely open, in that the pressure which is measured in the pressurized store (2) is compared with an expected pressure, which acts as a comparison value for the dynamic pressure, and in that the comparison is used to draw conclusions as to the ability of the pressure control valve (4) to function.
2. Method according to Claim 1, characterized in that the pressure in the pressurized store (2) is only measured following a waiting time after the pressure control valve (4) has been opened.
3. Method according to Claim 1 or 2, characterized in that the expected pressure is determined as a function of parameters of an intact pressure control valve (4).
4. Method according to one of Claims 1 to 3, characterized in that the expected pressure is determined as a function of current operating variables of the internal combustion engine.
5. Method according to one of Claims 1 to 4, characterized in that the pressure control valve is recognized as soiled if the measured pressure is greater than the expected pressure.
6. Method according to one of the preceding claims, characterized in that the internal combustion engine is in overrun mode or in idling mode.
7. Method according to one of the preceding claims, characterized in that the temperature and/or speed of the internal combustion engine is within a permissible range.
8. Electrical control element, in particular flash memory or read only memory, for a control unit (16) of an internal combustion engine, in particular in a motor vehicle, on which is stored a program which can run on a computer, in particular on a microprocessor, and is suitable for carrying out a method according to one of Claims 1 to 7.
9. Control unit (16) for a fuel supply system (1) of an internal combustion engine, in particular in a motor vehicle, in which fuel in the fuel supply system (1) is pumped by a pump (6, 10) into a pressurized store (2), the pressure (prist) in the pressurized store (2) can be measured, and the pressure (prist) in the pressurized store (2) can be changed by actuating a pressure control valve (4), characterized in that the pressure control valve (4) is completely opened by the control unit (16), in that the pressure measured is the dynamic pressure at the pressure control valve (4), on account of the pressure control valve (4) being completely open, in that the pressure which is measured in the pressurized store (2) is compared by the control unit (16) with an expected pressure, which acts as a comparison value for the dynamic pressure, and in that the comparison is used to draw conclusions as to the ability of the pressure control valve (4) to function.
10. Fuel supply system (1) for an internal combustion engine, in particular in a motor vehicle, in which fuel is pumped by a pump (6, 10) into a pressurized store (2), in which the pressure (prist) in the pressurized store (2) can be measured, and in which the pressure (prist) in the pressurized store (2) can be changed by actuation of a pressure control valve (4), and having a control unit (16), characterized in that the pressure control valve (4) is completely opened by the control unit (16), in that the pressure measured is the dynamic pressure at the pressure control valve (4), on account of the pressure control valve (4) being completely open, in that the pressure which is measured in the pressurized store (2) is compared by the control unit (16) with an expected pressure, which acts as a comparison value for the dynamic pressure, and in that the comparison is used to draw conclusions as to the ability of the pressure control valve (4) to function.

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