WO2017100871A1

WO2017100871A1 - Process for detecting internal fuel leakage in a combustion engine, and engine control unit

Info

Publication number: WO2017100871A1
Application number: PCT/BR2015/050254
Authority: WO
Inventors: Rafael Augusto AMEND DA CRUZ; Frederico Paulo TISCHER; Satish Patel
Original assignee: Robert Bosch Limitada
Priority date: 2015-12-14
Filing date: 2015-12-14
Publication date: 2017-06-22

Abstract

The present invention relates to a process for detecting internal fuel leakage in a combustion engine equipped with a lambda sensor (18), which includes the following steps: detecting an operating phase with no torque requirement; determining the measured value (22) of the lambda sensor; determining the expected theoretical value (23) of the lambda sensor; comparing the measured value (22) of the lambda sensor with the expected theoretical value (23) of the lambda sensor; activating a fuel leakage indicator if the comparison of the measured value (22) of the lambda sensor with the expected theoretical value (23) of the lambda sensor indicates a reduced concentration of oxygen. The invention also relates to an engine control unit which includes a program for implementing this process for detecting internal fuel leakage in a combustion engine.

Description

Report of the Invention Patent for "INTERNAL FUEL LEAK DETECTION PROCESS ON A COMBUSTION ENGINE AND ENGINE CONTROL UNIT",

[001] The present invention relates to the control of combustion engines and more specifically to strategies for increasing safe use and reducing emissions of polluting gases. The invention proposes a process of detecting internal fuel leakage in a combustion engine.

[002] For any fuel used in an engine, there is a risk of internal leakage, that is, a risk of fuel leakage within the engine cylinders due, for example, to a failure of an injector or valve.

[003] A leak detection process can be used to take steps to remedy these untimely emissions of gasified engine fuel, which can be hazardous and environmental damage. If leaking fuel is ignited, this leads to an unexpected rise in engine speed or torque, causing safety problems.

[004] If leaking fuel is not ignited, it leads to the escape of that unburnt fuel from the exhaust circuit, constituting an emission that may be an environmental pollutant. In addition, if the vehicle is equipped with a catalyst, that unburnt fuel can destroy the catalyst.

[005] This is the case, for example, if the fuel or one of the fuels used in the engine is compressed natural gas. With growing concern about greenhouse gas emissions, the use of natural gas as a fuel has been seen as a very interesting alternative. Natural gas, whose main component is methane due to its higher hydrogen to carbon ratio and high energy content, generates about 22% less carbon dioxide compared to diesel, considering the same combustion efficiency. In addition, reducing particulate emissions is very important and allows focused calibration in reducing nitrogen oxides. However, hydrocarbon emissions are higher than those of a typical diesel engine and consist mainly of methane.

[006] The main challenge in using compressed natural gas engines is to maintain a low level of methane emissions. Methane being one of the main greenhouse gases is crucial to prevent its emission into the atmosphere as a consequence of an internal leakage of natural gas in an engine.

Description of the prior art

EP1873378 describes a process of detecting fuel leakage in a combustion engine. A pressure sensor is used to detect a pressure drop in the engine's fuel supply ducts. A lamba sensor is also used to identify the type of fuel that is feeding the engine.

Brief Description of the Invention

[008] The purpose of the present invention is to improve known methods and devices.

To this end, the invention relates to a process of detecting internal fuel leakage in a combustion engine fitted with a lambda sensor. The process includes the following steps:

- detect an operating phase without torque demand;

- determine the value measured by the lambda sensor;

- determine the expected theoretical value of the lambda sensor;

- compare the value measured by the lambda sensor with the expected theoretical value of the lambda sensor;

- activate a fuel leakage indicator if the comparison of the measured value by the lambda sensor with the expected theoretical value of the lambda sensor indicates a reduced oxygen concentration.

[0010] The invention thus enables reliable detection of any fuel leakage in a combustion engine. For this, the process according to the invention uses only usual elements in a motor of modern combustion ok! like the lambda probe. No additional elements such as pressure sensors are required.

[001 1] At the safety level, leak detection and reaction prevents unexpected increases in vehicle speed.

The process may further include one of the following optional features, or a set of these combined features.

[0013] The torque-free operating phase is an overdrive phase.

[0014] The term "overrun" defines an operating phase of a vehicle engine in which:

- the vehicle is launched inertia or is going down a slope;

- The driver of the vehicle took his foot off the accelerator.

[0015] The torque-free operating phase is a idle phase.

[0016] The process includes an additional stepping-stone control step where any abnormal engine speed variation is detected during idling.

Activation of a fuel leakage indicator leads to activation of a light on the dashboard of the motor vehicle.

Activation of a fuel leak flag results in the closing of a safety valve to stop the fuel leak.

[0019] The step of determining the expected theoretical value of the lambda sensor is performed by mathematical calculation.

[0020] The step of determining the expected theoretical value of the lambda sensor is performed with a motor control map.

[0021] The step of determining the expected theoretical value of the lambda sensor is performed by computer modeling.

[0022] The process is applied to a multi-fuel engine and activation of a fuel leak flag leads to the switch to a single fuel mode. [0023] The invention thus allows a quick and safe reaction to a fuel leak and ensures the prevention of emissions of polluting gases.

Rapid detection and reaction to fuel leakage also prevents catalyst degradation which will lead to new environmental impacts due to higher emissions.

The invention also relates to a motor control unit which includes a program for performing the process described above and which includes a prediction module adapted to determine the expected theoretical value of the lambda sensor in a non-demand operating phase. of torque.

Taking advantage of the motor control unit's mathematical calculation capabilities makes it possible to add this leak detection function economically.

The motor control unit may include a prediction module adapted to determine the expected theoretical value of the lambda sensor in an operation phase without torque demand.

Brief Description of the Drawings

The invention is explained below by the description of a preferred embodiment, given by way of example, with reference to the figures in which:

Figure 1 is a schematic representation of a combustion engine adapted for the implementation of the invention;

Figure 2 is a graph illustrating the behavior of a normal idling engine;

Figure 3 is a graph illustrating the behavior of an idling engine during a gas leak incident;

Figure 4 is a graph illustrating the behavior of a normal-inertia engine driven by the vehicle's inertia;

Figure 5 is a graph illustrating the behavior of an inertial driven engine driven by the vehicle during a gas leak incident. Detailed Description of the Figures

The present preferred embodiment relates to a dual-fuel diesel engine - compressed natural gas.

The operation of this type of engine is based on the use of a pilot diesel fuel injection as a replacement for the spark of Otto cycle engines. Natural gas is introduced into the engine together with air through the intake duct.

In the admission cycle, the natural gas! mixed with air flows into the cylinder through the intake valves. In the compression cycle, the resulting mixture is compressed and a pilot diesel injection is performed. The increase in temperature and pressure allows self-ignition of diesel. In the combustion cycle, combustion of diesel ignites natural gas.

[0032] This type of dual-fuel diesel-compressed natural gas engine is known and therefore its operation need not be described in detail here.

Referring to figure 1, the bi-fuel diesel engine - natural gas! Compressed air includes a piston 1 mounted on a cylinder 2, and a combustion chamber 3. An inlet conduit 4 and an exhaust conduit 5 are connected to the combustion chamber 3 by means of valves 6. In this schematic view only An engine cylinder is shown.

This engine is powered by a diesel circuit 7 which includes a tank 8, a fuel pump 9, a common ramp 10 and diesel injectors 11.

The engine is also powered by a compressed natural gas circuit that includes a series of tanks 12, a pressure regulator and safety valve 13, and a gas injector 14 adapted to introduce a defined amount of gas into the fuel line. admission 4.

[0036] A motor control unit 15 is connected to the different motor sensors and actuators and performs motor control according to integrated motor control programs. The engine control unit

15 is connected to several classic sensors, including a lambda sensor

18 Engine control unit 15 includes an electronic gas control module 16 controlling gas injector 14 and an electronic diesel control module 17 controlling diesel injectors 1 1. The electronic gas control module 16 and the electronic diesel control module 17 can communicate with each other so that the engine can run in coordination with a mixture of diesel and gas.

The fuel leak detection process will now be described.

In the event of a malfunction, the gas injector 14 may, for example, be locked in an open position and therefore constantly leaking gas in the intake duct 4.

In this embodiment, leak detection is performed during two engine operating phases: the idling phase and the overdrive phase. These phases are chosen because they are the most favorable for such detection.

Leak detection takes advantage of the value measured by the lambda sensor. This value is representative of the level of oxygen concentration in the exhaust pipes. The Lamba sensor measures the difference between the amount of oxygen in the exhaust gas and the amount of oxygen in the open air for a given air-fuel ratio. the ratio of air mass to fuel mass in the air-fuel mixture at a given time.

The lambda sensor is a solid electrolyte made of ceramic material that becomes conductive at high temperatures and generates a characteristic galvanic voltage that is an index of the oxygen content of a gas.

Each time the engine is in idle or overdrive phase, engine control unit 15 will determine the value measured by the lambda sensor and compare this value with the expected theoretical value of the lambda sensor.

If the value measured by the lambda sensor is significantly lower than the expected theoretical value, it means that there is some hydrocarbon being oxidized in the exhaust duct 5. This is because the exhaust gases passing through the lambda sensor are subjected to high temperatures in this exhaust duct environment 5. With the presence of oxygen, the hydrocarbons present in these gases are oxidized, reducing the oxygen concentration. This surprising phenomenon leads to a reduction in oxygen concentration as a consequence of the presence of hydrocarbons in the exhaust gases.

Leak detection takes advantage of this phenomenon by comparing the value measured by the lambda sensor, which is modified by any leakage, and the expected theoretical value, which represents a normal situation without leakage.

The expected theoretical value can be stored or calculated for a given motor operating phase. This theoretical value is the characteristic value of normal operation that would be provided by the lambda sensor without the presence of natural gas.

In the case of the overdrive phase, the expected theoretical value rises to infinity because it is only air that passes through the exhaust duct.

In the case of the idling phase, the expected theoretical value can be calculated by modeling the engine characteristics, taking into account the minimum diesel injection required to keep the engine idling.

Any kind of known method can be used to determine the expected theoretical value of the lambda sensor for a given motor operating phase, such as computer modeling, motor control map, mathematical calculation.

Figures 2 to 5 illustrate different stages of engine operation. For each figure, the four curves represented are relative to the following engine quantities:

- engine speed (curve 20);

- Motor torque (curve 21);

- Value measured by lambda sensor (curve 22);

- Expected theoretical value of the lambda sensor (curve 23). With respect to the idling phase, figure 2 illustrates the typical behavior of the engine in this phase. Rotation 20 and torque 21 are kept at a minimum value. The engine is in a state where there is no torque demand and where torque is controlled by the engine control unit idle program 15.

Figure 2 shows that the value measured by the lambda sensor 22 and the expected theoretical value of the lambda sensor 23 are stable in the idle phase. Moreover, these values 22, 23 are similar, ie the measurement of oxygen concentration agrees with the expected oxygen concentration. Engine runs normally, no fuel leakage.

Figure 3 illustrates the behavior of the engine when a natural gas leak occurs, for example if the gas injector 14 fails and is constantly open. In this case, all air entering the engine arrives mixed with natural gas and engine control unit 15 is not aware of this.

In addition, engine control unit 15 detects an increase in engine speed 20 (as shown in the figure) and reacts by attempting to idle by reducing the amount of diesel injected. Consequently, the expected theoretical value of the lambda sensor 23 shows a significant rise (until it leaves the graph) because the motor control unit 15 thinks it is modifying the mixture to make it poorer. Injecting less diesel, engine control unit 15 expects a higher lambda value 23.

However, with gas leakage, unburned gas appears exiting the exhaust duct 5 and passing the lambda sensor, which causes the phenomenon of oxygen concentration reduction to appear as a consequence of the presence of hydrocarbons in the exhaust gases. . For this reason there is a drop in the actual value measured by the lambda sensor 22 as illustrated in figure 3.

The motor control unit 15 program analyzes this important difference between the value measured by the lambda sensor 22 and the expected theoretical value of the lambda sensor 23 as a gas leak symptom and reacts by activating a gas leak indicator. gas. [0058] In this example, the activated gas leak flag results in the shutoff of safety valve 13 to stop the gas leak. For this reason, the graph in figure 3 shows that the four curves 20, 21, 22, 23 return to normal after this period of leakage.

In the idling phase of the engine, leak detection can be completed by a control of the speed of rotation. As illustrated in figure 3, the leakage period is also characterized by an irregularity of rotation 20 and motor torque 21. Complementary detection of uneven rotation, that is, abnormal engine speed variation 20, can serve to confirm leak detection during idle phase.

With respect to the overdrive phase, Figure 4 illustrates typical engine behavior at this phase. The chart is completed by an overdrive curve 24 which, in a high position, indicates that the motor vehicle is in the overdrive phase, thus marking the beginning and end of this phase.

The overdrive phase begins, for example, when the driver of the self-propelled vehicle removes the accelerator foot. The vehicle continues to advance at its inertia and fuel injection is stopped,

[0062] Figure 4 shows that in the normal course of the overdrive phase, rotation 20 shows a slight decrease caused by the motor vehicle's speed loss, and torque 21 drops to zero because there is no external torque demand. As engine control unit 15 has stopped injecting any fuel, the value measured by the lambda sensor 22 rises to its maximum limit as only air passes through the engine. For the same reasons, the expected theoretical value of the lambda 23 sensor rises to infinity as it is a calculated theoretical value.

In this normal overdrive phase without fuel leakage, the measurement of oxygen concentration is identical to the expected oxygen concentration. The value measured by the lambda sensor 22 is identical to the expected theoretical value of the lambda sensor 23, as each of these curves reaches its respective limit. Figure 5 illustrates engine behavior when a natural gas leak occurs in this overdrive phase,

As described above for idle phase, gas injector 14 can fail and be constantly open so that all air entering the engine arrives mixed with natural gas without engine control unit 15 be aware of it.

The leak appears shortly after the value measured by the lambda sensor 22 reaches its maximum.

Shortly after the leak occurs, the phenomenon of oxygen concentration reduction appears as a consequence of the presence of hydrocarbons in the exhaust gases. Therefore, shortly after the leak occurs, the value measured by the lambda sensor 22 drops to a minimum value, similar to what it had before the overdrive phase.

There is then an alert interval 25 in which the expected theoretical value of the lambda sensor 23 is at its maximum while the value measured by the lambda sensor 22 has already fallen. In this warning interval 25, the engine control unit 15 analyzes this important difference between the measured value by the lambda sensor 22 and the expected theoretical value of the lambda sensor 23 as a gas leak symptom and reacts by activating a leak flag. of gas.

As for the idling phase, the activated gas leak flag results in a reaction measurement which may be, in this example of a dual-fuel engine, a change to a diesel-only mode, and closing the safety valve 13. The activated gas leakage indicator may also activate a light on the dashboard of the motor vehicle.

[0070] The method set out in this Article applies to all vehicles fitted with an exhaust-fueled or multi-fuel lambda sensor in the Otto or Diesel cycle.

Having described a preferred embodiment example, it should be understood that the scope of the present invention encompasses other possible variations, being limited only by the content of the appended claims, including the possible equivalents,

For example, in this embodiment, diesel injector 11 is a direct injector and gas injector 14 is an indirect injector, since the invention can be applied to any type of injector. Similarly, detection can be performed during other engine operating phases, other than idling and overdrive phase.

Claims

1 . Process for detecting internal fuel leakage in a combustion engine fitted with a lambda sensor (18), characterized in that it includes the following steps:

- detect an operating phase without torque demand;

- determining the value measured by the lambda sensor (22);

- determine the expected theoretical value of the lambda sensor (23);

- comparing the value measured by the lambda sensor (22) with the expected theoretical value of the lambda sensor (23);

- activating a fuel leakage indicator if comparing the value measured by the lambda sensor (22) with the expected theoretical value of the lambda sensor (23) indicates a reduced oxygen concentration.

Leak detection process according to claim 1, characterized in that the torque-free operating phase is an overdrive phase,

A leak detection process according to claim 1, characterized in that the torque-free operating phase is a idling phase.

Leak defect method according to Claim 3, characterized in that it includes an additional step of control of the rotation regularity in which any abnormal variation of engine speed (20) is detected during the running phase. slow.

Leak detection method according to any one of claims 1 to 4, characterized in that the activation of a fuel leakage indicator leads to the activation of a light indicator on the dashboard of the motor vehicle.

Leak detection method according to any one of claims 1 to 5, characterized in that the activation of a fuel leakage signal leads to the closing of a safety valve (13) to stop the fuel leakage.

A leak detection method according to any one of claims 1 to 6, characterized in that the step of determining the leakage Expected theoretical value of the lambda sensor (23) is performed by mathematical calculation.

A leak detection method according to any one of claims 1 to 6, characterized in that the step of determining the expected theoretical value of the lambda sensor (23) is performed with a motor control map.

A leak detection method according to any one of claims 1 to 6, characterized in that the step of determining the expected theoretical value of the lambda sensor (23) is performed by computer modeling.

A leak detection method according to any one of claims 1 to 9, characterized in that the process is applied to a multi-fuel engine and that activation of a fuel leak signaling device leads to the switch to a single fuel mode.

1 1. Motor control unit characterized by the fact that it includes a program for the execution of the process as defined in any one of claims 1 to 10, and which includes a prediction module adapted to determine the expected theoretical value of the lambda sensor (23) at an operation phase without torque demand.

Engine control unit according to Claim 11, characterized in that it includes an electronic gas control module (16) controlling compressed natural gas injectors (14) and an electronic diesel control module. (17) controlling diesel injectors (11) which can communicate with one another.