WO2014168564A1

WO2014168564A1 - Monitoring unit and method for monitoring a fuel system

Info

Publication number: WO2014168564A1
Application number: PCT/SE2014/050426
Authority: WO
Inventors: Dan CEDFORS; Kim KYLSTRÖM
Original assignee: Scania Cv Ab
Priority date: 2013-04-09
Filing date: 2014-04-07
Publication date: 2014-10-16
Also published as: SE1350440A1; DE112014001033T5; BR112015020748A2; SE539216C2; DE112014001033B4

Abstract

The invention pertains to a method and a device for monitoring a fuel system (4) in a combustion engine (6). According to the invention, the fuel system comprises a fuel pump (10) which may be operated independently of the engine's engine speed, and sensors (18, 20) to measure the level in the fuel tank and the pressure and/or flow in the fuel conduit (13). A monitoring device (2) receives values from the sensors and compares them with stored, expected values. If any measured value differs from the expected value, an indication signal (28) may be sent to attract the attention of the driver or staff at a garage to a potential leakage in the fuel system.

Description

Monitoring unit and method for monitoring a fuel system

Field of the invention

The present invention pertains to a monitoring unit and a method in connection with a monitoring unit, according to the preambles of the independent patent claims.

The monitoring unit and the method according to the invention are specifically adapted to be applied in connection with vehicles, for example trucks and buses, but may also be used in other applications where combustion engines are used, for example on board ships and in industry.

Background of the invention

Combustion engines burn an air/fuel-mixture in several cylinders, in order to operate pistons that generate a driving torque. Air is sucked into a suction conduit through an inlet and fuel is then injected into the suction conduit or directly into the cylinders (direct injection) in order to create the air/fuel-mixture. A fuel system is used to adapt the fuel flow which is injected, in order to obtain a desired air/fuel- mixture for the cylinders.

The fuel system often contains one or several fuel tanks, fuel pumps and fuel injection devices. For example, a low pressure fuel pump may extract the fuel from a fuel tank, pressurise the fuel and supply fuel with low pressure to an injection device or a high pressure fuel pump.

A high pressure fuel pump increases the pressure further and forwards the fuel to one or several injection devices.

US-2010/0326413 pertains to a system and a method to protect a fuel pump, among others based on control of whether the pump delivers the correct amount of fuel.

US-2011/0224888 pertains to a method to diagnose faults in a fuel injection system, which comprises sending in a specific amount of fuel and detecting the torque from the engine. If this differs from the expected value, the fuel system is deemed to be faulty.

RECORD COPY TRANSLATION

(Rule 12.4) DE-102004005851 pertains to a method to diagnose faults in a fuel system. While starting or turning off a combustion engine, the pressure change is measured in the fuel conduit after the fuel pump. If this differs from the expected value, the fuel system is deemed to be faulty.

Current vehicles often have a mechanical fuel pump arranged in connection with the vehicle's combustion engine, where the fuel pump is operated by the engine. Such a mechanical fuel pump provides a flow which is directly dependent on the engine's speed. This is not always desirable, since it entails, for example, that the fuel flow may be higher than desired at higher engine speeds.

Current low pressure systems do not provide for any possibility of detecting fuel leakages other than through visual detection of leaking fuel on the ground.

A smaller leakage is even more difficult to detect since the vehicle's performance is not noticeably impacted.

There is a need to improve the detection of faults in fuel systems for e.g. vehicles, in particular cargo vehicles which are often driven during very long periods, and in particular to discover irregularities in the fuel flow from the tank to the engine. The objective of the present invention is to achieve an improved detection of faults in fuel systems, and in particular an improved detection of fuel leakages from the fuel system.

Summary of the invention

The above-mentioned objectives are achieved with the invention as defined by the independent patent claims.

The preferred embodiments are defined by the dependent patent claims. The present invention is applicable in a fuel system of a type that may be called a controllable low pressure system, wherein the pumping of fuel is controlled independently of the engine in for example a vehicle. According to the invention, a control with respect to leakages may be carried out before each start or during operation, with the computation of amount in relation to sensor values from a level sensor and pressure/flow sensors and defined benchmarks. The control may result in the generation of an indication signal, which may lead to/request manual control or driving to a garage.

The present invention thus improves the possibility of detecting and diagnosing an irregularity in the fuel flow between the engine and the tank, which in particular may occur in the event of a fuel leak in a low pressure part of a fuel system.

Brief description of drawings

Figure 1 is a schematic block diagram which illustrates the present invention. Figure 2 is a schematic block diagram which illustrates one embodiment of the present invention.

Figure 3 is a schematic image of a vehicle, where the present invention has been implemented.

Figure 4 is a flow chart which schematically shows the method according to the present invention.

Detailed description of preferred embodiments of the invention

In the figures, details with the same or similar functions and adaptation have consistently received the same reference numerals. In many vehicles today, the fuel pump is arranged in connection with the engine, and sucks up the fuel. Often, the fuel pump is mechanically connected to the engine and operated independently of the engine's driving shaft.

In another type of fuel system for combustion engines, the fuel pump is instead arranged in connection with the main tank and pressurises the fuel via fuel conduits to the engine. In this type of fuel system, the fuel pump is often

electrically, pneumatically or hydraulically driven, and is operated independently of the movements of the combustion engine's driving shaft. The present invention is applicable to this second type of fuel system, i.e. wherein the fuel pump is arranged in connection with the main tank and pushes the fuel to the engine. The fuel pump is for example electrically, pneumatically or

hydraulically operated, independently of the movements of the combustion engine's driving shaft.

According to one variant, there is a smaller transfer pump arranged to pump fuel from one or several main tanks to a smaller tank. In connection with the smaller tank, there is a main pump arranged to subsequently pump along the fuel from the smaller tank to the engine, via for example a high pressure pump, which is often arranged in connection with the engine.

One reason for arranging a smaller tank, and for pumping the fuel via this tank, is that when driving in hilly terrain the fuel may gather in large tanks, so that the fuel armature is not able to suck up the fuel if there is relatively little fuel left in the tank.

The present invention will now be described in detail with reference to the figures.

First, with reference to figures 1 and 2, relating to block diagrams showing two embodiments of a monitoring unit 2 in connection with a fuel system 4 for a combustion engine 6. The fuel system 4 comprises a fuel tank system 8 with at least one main tank 9 (figure 2) intended for fuel. Further, at least one fuel pump 10 is arranged in connection with the main tank 9, and a control device 12 is adapted to control pumping of the fuel from the fuel tank system 8 to the combustion engine 6 via a fuel conduit 13, by the means of a control signal 14 to the fuel pump 10. In the figure, the fuel pump 10 has been illustrated as being located outside the main tank 9. According to one variant, the fuel pump 10 is instead arranged in the main tank 9. The monitoring unit 2 is adapted to receive at least two sensor signals 16. First, at least one sensor signal 16 from the pressure- and/or flow-sensors 18, adapted to measure the pressure and/or flow of the fuel in the fuel conduit 13, preferably after said fuel pump 10. Second, at least one sensor signal 16 from one or several level sensors 20 in the fuel tank system 8, adapted to measure a fuel level in said main tank 9. These sensor signals 16 contain sensor values from said sensors (18, 20). The monitoring unit 2 is also adapted to receive a mode signal 22 specifying which fuel system mode, see below, of at least two fuel system modes, the fuel system 4 is in. The mode signal 22 is generated, according to one embodiment, by the control device 12.

The monitoring unit 2 also comprises an analysis unit 24 and a memory unit 26. The analysis unit 24 is adapted to compare one or several values in a received set of sensor values with one or several values in a set corresponding to expected values, related to the given fuel system mode stored in the memory unit 26.

Further, the analysis unit is adapted to generate an indication signal 28 depending on the result of this comparison.

The indication signal may for example warn the driver that a fault has been detected, but may also contain information about the type of fault being present, e.g. if a leakage has been identified. This may also entail that error codes are generated, which may be read at a garage visit. If the fault is serious, an identified fault may entail that control signals are generated, causing the power of the engine to drop.

In the analysis unit, a received sensor value is thus compared to an expected sensor value, for example by forming a difference between these values and analysing the size of this difference taking into consideration relevant fuel system mode. The analysis unit 24 is preferably adapted to generate said indication signal if the comparison exceeds predetermined discrepancy thresholds. Such discrepancy thresholds are also stored in the memory unit 26.

The comparison made may for example indicate that the sensor values from the level sensors show that the fuel level in the tanks is falling, while sensor values from the pressure sensor in the fuel conduit after the fuel pump fail to show pressure values which should obtain when the fuel level is dropping as indicated by the level sensors. This may indicate some fault in the fuel system, for example an irregularity in the fuel flow from the fuel tank system to the combustion engine, which may be caused by a fuel leak.

The fuel system is thus adapted to be in one of a number of fuel system modes. This comprises a first fuel system mode which obtains when the fuel system 4 is activated in accordance with a predetermined activation schedule. The activation of the fuel system may for example occur when the vehicle is to be started and used. This may be initiated when the driver door is opened, when the vehicle is unlocked, when the driver sits in the driver seat, or when the key is inserted.

In connection with the activation, a predetermined activation schedule is followed, entailing that the fuel pump or pumps are activated, and for example increase the pressure of the fuel inside the fuel conduit. The increase of the pressure should occur in a predetermined prior art manner, for example by following a ramp, during a specified time period.

A second fuel system mode exists in the fuel system 4 when the combustion engine 6 is in a normal operating state. Normal operating states may mean that the vehicle is driven with a substantially constant speed and substantially constant driving resistance, or idling. The expected sensor values from the pressure sensors for this mode should then for example remain at a relatively low value while the sensor values from the level sensor should at the same time indicate a certain expected drop of this level. A third fuel system mode exists in the fuel system 4 when the combustion engine is dragged, i.e. the engine is turned by the drive line without any fuel supply.

When the engine is dragged, the expected sensor values from the pressure sensors and the sensor values from the level sensors should remain at a relatively constant value. Alternatively, when the engine is dragged a schedule with a pressure increase similar to the one in the first fuel system mode may be initiated.

For heavy goods vehicles the operating hours are often long. There may be several days between shut-downs. It is therefore essential to be able to monitor the fuel system during operation.

The monitoring device 6 is adapted to receive said sensor signals 16 at a predetermined reading interval which is customized to the values to be read. This means that sensor values from level measurement do not need to be read as often as pressure or flow values. The reading may naturally also occur in an essentially continuous way.

The analysis unit is adapted to carry out comparisons with a predetermined analysis interval, which is sufficiently brief in order to identify relevant changes. The interval may be in the range of one or a number of seconds.

The memory unit 26 preferably comprises a database with said expected corresponding values related to said fuel system modes. These have initially been determined taking into consideration the specifications of the fuel system and the engine. For example, tabulated values may exist for associated pressures, flows, levels in relation to the pumps' operation.

The analysis unit 24 is adapted to preferably update said expected associated values for fuel system modes depending on historical values. In other words, the analysis unit is adapted to adaptively update these values depending on how the system behaves. The monitoring system is preferably adapted to a fuel system, wherein said at least one fuel pump 10 is electrically, pneumatically or hydraulically driven.

Figure 2 shows a block diagram of a type of fuel system where the fuel tank system 8 comprises two main tanks 9. These are connected with each other so that fuel may flow from the right main tank to the left main tank in the figure.

A transfer pump 32 is arranged to pump fuel from the main tank 9 to a transfer tank 30, which is significantly smaller than the main tanks. In the transfer tank 30, the fuel pump 10 is arranged. Both the transfer pump 32 and the fuel pump 10 are controlled by control signals 14 from the control device 12. It should be noted that the transfer pump 32 may alternatively be arranged in the main tank 9, and that the fuel pump 10 may alternatively be arranged outside the transfer tank 30.

Figure 3 shows a schematic image of a vehicle 34, comprising a combustion engine 6, a fuel system for the combustion engine, wherein the fuel system comprises a fuel tank system 8 with a main tank intended for fuel, at least one fuel pump 10 arranged in connection with the main tank and a control device 12 adapted to control the pumping of fuel from the fuel tank system to the

combustion engine. Further, a monitoring unit 2 is arranged and functions in accordance with the description above.

The present invention also pertains to a method for monitoring with a monitoring unit in accordance with the description above. The monitoring unit is thus adapted to be arranged in connection with a fuel system for a combustion engine. The fuel system comprises a fuel tank system with at least one main pump intended for fuel, at least one fuel pump arranged in connection with the main tank and a control device adapted to control pumping of the fuel from the fuel tank system to the combustion engine via a fuel conduit, by the means of a control signal to the fuel pump.

The method will now be described with reference to the flow chart in Fig. 4. The method comprises the following steps: A to receive, in the monitoring unit, at least two sensor signals from pressure and/or flow sensors adapted to measure pressure and/or flow of fuel in the fuel conduit, preferably after said fuel pump, and from one or several level sensors in the fuel tank system adapted to measure a fuel level in said main tank, wherein said sensor signals comprise sensor values from aid sensors,

B to receive, in the monitoring unit, a mode signal which specifies which fuel system mode, of at least two fuel system modes, the fuel system is in, C to compare in an analysis unit in the monitoring unit, one or several values in a received set of sensor values with one or several values in a set of expected corresponding values, stored in a memory unit, related to the relevant fuel system mode,

D to generate an indication signal depending on the result of this comparison. The method entails that said indication signal preferably is generated by the analysis unit if the comparison exceeds predetermined discrepancy thresholds. According to one embodiment, the indication signal is adapted to indicate an irregularity in the fuel flow from the fuel tank system to the combustion engine, caused by for example a fuel leak.

As described above, the fuel system may operate in a number of fuel system modes. These comprise a first fuel system mode, obtaining when the fuel system is activated in accordance with a predetermined activation schedule, a second fuel system mode, obtaining in the fuel system when the combustion engine is in a normal operating state and a third fuel system mode, obtaining in the fuel system when the combustion engine is dragged.

The expected corresponding values related to the fuel system modes are stored in a database in a memory unit arranged in said monitoring device. These values may be updated dynamically by said analysis unit, depending on historical values. The invention also comprises a computer program in vehicles, wherein said computer program comprises program code to cause a monitoring unit, or a computer connected to a monitoring unit, to carry out the steps according to the method described above,

The present invention is not limited to the above-described preferred

embodiments. Various alternatives, modifications and equivalents may be used. The embodiments above shall therefore not be deemed to limit the scope of the invention, which is defined by the enclosed patent claims.

Claims

Patent claim

1. A method for monitoring with a monitoring unit in connection with a fuel system for a combustion engine, wherein the fuel system comprises a fuel tank system with at least one main tank intended for fuel, at least one fuel pump arranged in connection with the main tank and a control device adapted to control the pumping of fuel from the fuel tank system to the combustion engine via a fuel conduit, by means of a control signal to the fuel pump,

characterised in that the method comprises the following steps:

to receive, in the monitoring unit, at least sensor signals from pressure and/or flow sensors, adapted to measure pressure and/or flow of fuel in the fuel conduit, preferably after said fuel pump, and from one or several level sensors in the fuel tank system, adapted to measure a fuel level in said main tank, wherein said sensor signals comprise sensor values from said sensors,

to receive, in the monitoring unit, a mode signal which specifies which fuel system mode, of at least two fuel system modes, the fuel system is in, wherein said fuel system modes at least comprise a first fuel system mode which obtains when the fuel system is activated in accordance with a predetermined activation schedule, and a second fuel system mode, which obtains in the fuel system (4) when the combustion engine (6) is in a normal operating state,

- to compare in an analysis unit in the monitoring unit, one or several values in a received set of sensor values with one or several values in a set of expected corresponding values, stored in a memory unit, related to the relevant fuel system mode,

to generate an indication signal depending on the result of this comparison.

2. Method according to claim 1 , wherein said indication signal is generated by the analysis unit if the comparison exceeds predetermined discrepancy thresholds.

3. Method according to claim 1 or 2, wherein said indication signal indicates a discrepancy in the fuel flow from the fuel tank system to the combustion engine.

4. Method according to any of the previous claims, wherein said fuel system modes comprise, in addition to a first fuel system mode obtaining when the fuel system is activated in accordance with a predetermined activation schedule and a second fuel system mode, obtaining in the fuel system (4) when the combustion engine (6) is in a normal operating state, a third fuel system mode, obtaining in the fuel system 4 when the combustion engine is dragged.

5. Method according to any of the previous claims, wherein said expected corresponding values related to said fuel system modes are stored in a memory unit arranged in said monitoring unit.

6. Method according to any of the previous claims, wherein said expected corresponding values for fuel system modes are adapted to be updated dynamically by said analysis unit, depending on historical values.

7. Computer program in vehicles, wherein said computer program comprises program code to cause a monitoring unit (2), or a computer connected to a monitoring unit (2), to carry out the steps according to the method in accordance with any of claims 1-6.

8. Monitoring unit (2) for a fuel system (4) for a combustion engine (6), wherein the fuel system (4) comprises a fuel tank system (8) with at least one main tank (9) intended for fuel, at least one fuel pump (10) arranged in connection with the main tank (9) and a control device (12) adapted to control pumping of the fuel from the fuel tank system (8) to the combustion engine (6) via a fuel conduit (13), by means of a control signal (14) to the fuel pump (10),

characterised in that the monitoring unit (2) is adapted to receive

- at least two sensor signals (16) from pressure and/or flow sensors (18) adapted to measure pressure and/or flow of fuel in the fuel conduit (13), preferably after said fuel pump (10), and from one or several level sensors (20) in the fuel tank system (8) adapted to measure a fuel level in said main tank (9), wherein said sensor signals (16) comprise sensor values from said sensors (18, 20), the monitoring unit (2) also being adapted to receive

- a mode signal (22) which specifies which fuel system mode, of at least two fuel system modes, the fuel system (4) is in, wherein said fuel system modes comprise at least one first fuel system mode which obtains when the fuel system (4) is activated in accordance with a predetermined activation schedule and a second fuel system mode, which obtains in the fuel system (4) when the combustion engine (6) is in a normal operating state;

the monitoring unit (2) also comprising an analysis unit (24) and a memory unit (26), wherein said analysis unit (24) is adapted to compare one or several values in a received set of sensor values with one or several values in a set of

corresponding expected values related to the relevant fuel system mode stored in the memory unit (26), and to generate an indication signal (28), depending of the result of this comparison.

9. Monitoring unit (2) according to claim 8, wherein the analysis unit (24) is adapted to generate said indication signal if the comparison exceeds

predetermined discrepancy thresholds.

10. Monitoring unit (2) according to claim 8 or 9, wherein said indication signal is adapted to indicate an irregularity in the fuel flow from the fuel tank system (8) to the combustion engine (6).

1 1 . Monitoring unit (2) according to any of claims 8-10, wherein said fuel system modes comprise, in addition to a first fuel system mode obtaining when the fuel system (4) is activated in accordance with a predetermined activation schedule and a second fuel system mode, obtaining in the fuel system (4) when the combustion engine (6) is in a normal operating state, a third fuel system mode, obtaining in the fuel system 4 when the combustion engine is dragged.

12. Monitoring unit (2) according to any of the claims 8-1 1 , wherein said memory unit comprises a database with said expected corresponding values related to said fuel system modes.

13. Monitoring unit (2) according to any of claims 8-12, wherein said analysis unit (24) is adapted to update said expected associated values for fuel system modes, depending on historical values.

14. Monitoring unit (2) according to any of the claims 8-13, wherein said at least one fuel pump (10) is electrically, pneumatically or hydraulically driven.

15. Combustion engine (6) comprising a fuel system for the combustion engine, wherein the fuel system comprises a fuel tank system with a main tank intended for fuel, at least one fuel pump arranged in connection with the main tank and a control device adapted to control the pumping of fuel from the fuel tank system to the combustion engine, wherein the vehicle comprises a monitoring unit according to any of patent claims 8-14.

16. A vehicle (34) comprising a combustion engine (6) according to claim