KR100765640B1 - Misfire diagnosis controlling method of lpi engine - Google Patents

Abstract

A misfire diagnosis controlling method of a liquefied petroleum injection engine is provided to solve a misfire diagnosis error by preventing misfire diagnosis when a fuel level is lower than a reference level. A misfire diagnosis controlling method of a liquefied petroleum injection engine includes receiving a current fuel pressure and a current fuel temperature from a fuel pressure sensor and a fuel temperature sensor, calculating a saturation vapor pressure from the current fuel pressure and the current fuel temperature and a pressure margin depending on the current fuel pressure and the current fuel temperature, and comparing the current fuel pressure with a sum of the saturation vapor pressure and the pressure margin to determine that the fuel pressure is normal when the current fuel pressure is higher than the sum of the saturation vapor pressure and the pressure margin and determine that the fuel pressure is abnormal when lower than the sum.

Description

MILPIRE DIAGNOSIS CONTROLLING METHOD OF LPI ENGINE}

1 is a cross-sectional view showing an injector applied to the LPI engine,

2 is a view showing an example in which engine misfire occurs due to the opening of the cutoff solenoid valve in the PCD starting condition;

3 is a conceptual diagram showing the configuration of the LPI system to which the present invention is applied and the misfire diagnosis control process of the present invention;

4 is a flowchart showing a process of determining whether the normal pressure in the present invention,

5 is a saturated steam pressure diagram according to fuel temperature and composition.

<Explanation of symbols for main parts of the drawings>

1: fuel tank 2: fuel line

3: injector 4: fuel pressure sensor

5: fuel temperature sensor 6: IFB ECU

7: engine ECU

The present invention relates to a misfire diagnosis control method of an LPI engine, and more particularly, in order to solve a problem in which a misfire due to an engine misfire due to a vehicle failure occurs in a low fuel level state in an LPI system, a sensor mounted in a vehicle By monitoring the fuel pressure in real time and prohibiting misfire diagnosis when the monitored current fuel pressure is lower than the normal level. It relates to a misfire control method of the LPI engine that can be solved.

In general, the LPG engine is configured to vaporize the fuel supplied from the Bombe through a mixer and a vaporizer to supply the engine.

However, in the system using the mixer and the evaporator as described above, it is difficult to start the winter in the ECU because it is difficult to precisely control by the ECU, the power performance and fuel economy is low, and the instability of the children due to the failure of the maintenance cycle of the consumer due to the tar problem of LPG fuel Various problems occurred, such as a startup off phenomenon.

In order to solve these various problems, the proposed technology is the LPI engine.

Unlike conventional LPG engines that push fuel with only steam pressure of fuel, LPI (Liquefied Petroleum Injection) engine installs fuel pump in LPG cylinder to pump liquid LPG fuel through fuel supply line and then injector from engine. It is a system configured to inject through (Injector).

In other words, the LPI engine adopts a method of directly injecting LPG, which is fuel like a gasoline engine, into the combustion chamber through an injector. Instead of using a mixer and an evaporator, the LPI engine supplies LPG to the combustion chamber by precise control of the ECU through an injector. It is a system that can completely solve the old problems of LPG vehicles such as fuel efficiency, power performance, winter start-up, and maintenance cycle complaints.

In the first LPI system, as the durability progressed, leakage occurred in the injector, causing deterioration of startability and increasing HC (Hydro-Carbon) emissions.

Accordingly, the cutoff solenoid valve is installed at the bottom of the injector to improve the leakage problem.

1 is a cross-sectional view illustrating an injector applied to an LPI engine, and a cut-off solenoid valve 13 is disposed at an inner lower end of the injector 10 to prevent LPG gas from leaking when the engine is stopped. It is installed.

The cut-off solenoid valve 13 includes a plunger valve member 14 for opening and closing the fuel passage inside the injector and a solenoid 15 for operating the plunger valve member 14 when power is applied.

The cut-off solenoid valve 13 prevents the LPG gas from flowing into the combustion chamber through the intake manifold and the surge tank when the engine is stopped, thereby preventing the large amount of exhaust gas from being restarted. It is a technique applied to.

In FIG. 1, reference numeral 11 denotes a fuel supply port into which fuel is injected, and reference numeral 12 denotes a nozzle tip in which fuel is injected.

The injector 10 shown in the LPI engine has the same basic structure as compared to a gasoline injector, but the pressure of the internal fuel is maintained at a higher pressure than the gasoline injector, and the internal fuel is always kept at room temperature during soaking. As the weather is maintained, leakage occurs as the durability progresses.

Therefore, in order to prevent fuel leaked from the injector from leaking into the manifold during soaking, the cut-off solenoid valve 13 is mounted at the lower end of the injector 10, and the cut-off solenoid valve 13 during soaking. ) To block leakage and to open the cut-off solenoid valve during start-up and engine operation to allow fuel injection.

In this way, by mounting the cut-off solenoid valve in the lower end of the injector it is possible to solve the problem of fuel leakage caused by the injector.

However, a problem arises that misfire occurs due to a difference in fuel injection amount depending on the degree of opening of the cutoff solenoid valve, and furthermore, when the cutoff solenoid valve is not opened, misfire occurs continuously, which may cause catalyst damage.

In particular, a serious problem occurs due to the unopening of the cut-off solenoid valve during partial cool-down (PCD) start-up. The PCD start-up refers to starting after parking with the engine sufficiently warmed up.

While running, the engine temperature is maintained at a constant temperature by the cooling fan and running wind, but during parking, the temperature in the engine room starts to rise sharply, and after about 30 minutes, the temperature of the injector and cut-off solenoid rises to 90 ° C or higher. do.

In addition, the fuel line temperature rises above 80 ° C, so the fuel pressure in the injector and fuel line reaches its peak.

In addition, when the temperature of the cutoff solenoid increases, the resistance of the coil increases, and as the coil resistance increases, the magnetic force of the solenoid decreases.

Thus, the pressure across the cut off solenoid valve rises and the solenoid magnetic force decreases, thus reaching the worst condition in opening the cut off solenoid valve.

As a result, conventionally, the cutoff solenoid valve was not opened in the PCD starting condition as described above, and misfire occurred. In FIG. 2, the single cutoff solenoid valve was not opened in the PCD starting condition. It is a figure which shows the example of the state which generate | occur | produced.

The problem of not opening the cut-off solenoid at the start of the PCD can be improved by increasing the capacity of the cut-off solenoid (coil winding number) and reducing the cross-sectional area of the cut-off solenoid valve (reduced pressure area). There is a need for a method for detecting the open state of the cut-off solenoid when a failure occurs due to the progress of durability.

The unopening of the cut-off solenoid valve can be caused not only by electrical faults (disconnected / shorted) but also by various mechanical causes such as the aforementioned problems.

Therefore, in order to detect whether the cut-off solenoid valve is not opened due to mechanical problems, misfire diagnosis, which is an OBD-2 item, is essential.

However, even when the fuel is insufficient, misfire may occur due to a poor fuel supply when turning sharply or when the fuel is in a ground state.

This is not a problem with the system but a temporary misfire due to lack of fuel. Therefore, all EMS (Engine Management System) prohibits misdiagnosis under low fuel condition (usually 15% or less).

In cars subject to OBD-2 (On Board Diagnosis 2) regulation, the engine ECU receives fuel level from the fuel tank and prohibits misfire diagnosis when the fuel level is low. However, LPI vehicles are not subject to OBD-2 regulation. Do not receive fuel level input.

In the case of gasoline vehicles, the engine ECU receives a signal from the fuel level sensor installed in the fuel tank and prohibits misfire diagnosis when the fuel level is low.This prevents vehicle failure (mechanical failure of the system) when the fuel level is low. This prevents misdiagnosis due to engine misfire.

Therefore, unlike gasoline vehicles that are subject to OBD-2, new measures are needed to prohibit misdiagnosis at low fuel levels in LPI vehicles.

Accordingly, the present invention has been invented in consideration of the above-mentioned points, and in order to solve the problem of misdiagnosis due to engine misfire due to a vehicle error when the LPI system is in a low fuel level state, sensors mounted on the vehicle are used. Real-time monitoring of fuel pressure and prohibition of misfire diagnosis when the monitored current fuel pressure is lower than normal level, solves the problem of misdiagnosis caused by engine misfire due to vehicle abnormality at low fuel level. The purpose of the present invention is to provide an anti-fire control method of LPI engine.

Hereinafter, the present invention will be described in detail with reference to the accompanying drawings.

In order to achieve the above object, the present invention includes the steps of receiving the fuel pressure and the fuel temperature from the fuel pressure sensor and the fuel temperature sensor installed in the fuel line IFB ECU; Determining whether the fuel pressure is normal based on the current fuel pressure, fuel temperature, and fuel composition learning value received by the IFB ECU; The IFB ECU transmitting to the engine ECU whether the fuel pressure is normal; The engine ECU performs misfire diagnosis only when the fuel pressure is normal according to whether the fuel pressure is normal, and prohibits misfire diagnosis when the fuel pressure is abnormal.

The determining of whether the fuel pressure is normal by the IFB ECU may include calculating a current fuel pressure and a saturated steam pressure at a fuel temperature according to fuel composition; Calculating a pressure margin according to the current fuel pressure and the fuel temperature; Comparing the current fuel pressure with the calculated sum of saturated steam pressure and pressure margin, it is determined that the fuel pressure is normal if the current fuel pressure is more than the sum of saturated steam pressure and pressure margin, and if the fuel pressure is lower than the sum of saturated steam pressure and pressure margin, the fuel pressure is abnormal. Determining to be; characterized in that consisting of.

FIG. 3 is a conceptual diagram illustrating a configuration of an LPI system to which the present invention is applied and a true diagnosis process of the present invention, and FIG. 4 is a flowchart illustrating a normal pressure determination process in the present invention.

Hereinafter, the present invention will be described in more detail with reference to the accompanying drawings.

Fuel pressure Monitoring  Prohibition of true story diagnosis through

The reason that misfire occurs at low fuel level is because the fuel supply is not smooth and the injection fuel amount is insufficient as the fuel pressure drops excessively.

Therefore, if the fuel pressure falls below the normal level by using the fuel pressure instead of the fuel level, misfire diagnosis can be prohibited.

The LPI system is equipped with a fuel pressure sensor and a fuel temperature sensor in the fuel line to correct the fuel amount according to the fuel pressure.

Fuel pressure Monitoring  Prohibition of true story diagnosis through

In the LPI system, the fuel pressure sensor / fuel temperature sensor value is input to the IFB (InterFace Box) ECU 6 instead of the engine ECU 7.

Therefore, the engine ECU 7 in charge of misfire diagnosis cannot directly know the fuel pressure state, and therefore, the IFB ECU 6 should play a role of determining whether the normal pressure is present.

The IFB ECU 6 is an ECU that is responsible for actuator control and fuel input of fuel supply and injection systems such as the injector 10, the fuel pump 2, the fuel pressure sensor 4 / fuel temperature sensor 5, and the engine. The engine is driven by the exchange of information with the ECU 7 via CAN.

In the case of gasoline engines, the engine ECU does all the work such as fuel supply / injection control, ignition timing control, air volume control, and OBD diagnosis.In the LPI engine, fuel supply / injection control is performed by the engine ECU instead of the IFB ECU6. The document transmits the calculated fuel amount to the IFB ECU 6.

In the case of LPG, it is impossible to determine whether the fuel pressure is normal simply by the fuel pressure itself.

Because the saturated steam pressure is different depending on the fuel composition and the fuel temperature, the propane (low boiling point) ratio is high even at the same pressure, and when the fuel temperature is high, it may change from a relatively high fuel temperature to the gas phase, causing misfire due to insufficient fuel injection.

5 is a saturated steam pressure diagram according to fuel temperature and composition, and since the vaporization of fuel occurs when the pressure of the fuel line approaches the saturated steam pressure, the risk of misfire is high.

Therefore, the IFB ECU 6 calculates the current fuel pressure according to the fuel composition and the saturated steam pressure at the fuel temperature based on the signals of the fuel pressure sensor 4 and the fuel temperature sensor 5 installed in the fuel line 3, In addition, by calculating the pressure margin according to the current fuel pressure and fuel temperature, it can be determined as an abnormal pressure when the current fuel pressure is lower than the value of 'saturated vapor pressure + pressure margin' calculated as described above, and whether the pressure is abnormal By sending to the engine ECU 7 (using CAN communication), the engine ECU can prohibit misfire diagnosis at abnormal fuel pressure.

In saturated steam pressure, the gas phase and liquid phase coexist, so the margin must be set higher than the actual saturated steam pressure for sufficient liquefaction.

3 is a conceptual diagram of the present invention, 1 denotes a fuel tank, 4 denotes a fuel pressure sensor, 5 denotes a fuel temperature sensor, 10 denotes an injector, 6 denotes an IFB ECU, and 7 denotes an engine ECU.

As shown, the present invention is a process in which the IFB ECU 6 receives the fuel pressure and fuel temperature of the fuel line 3 from the fuel pressure sensor 4 and the fuel temperature sensor 5, IFB ECU 6 is A process of determining whether or not the normal pressure is determined based on the input fuel pressure, fuel temperature, and fuel composition learning value, a process of transferring whether the normal pressure determined by the IFB ECU 6 to the engine ECU 7 through CAN communication, and the engine The ECU 7 includes a process of determining whether misfire diagnosis is prohibited according to the normal pressure.

Here, with respect to the fuel composition learning value, the current LPI system has a function of modeling fuel composition through fuel pressure and fuel temperature under specific conditions.

4 is a flow chart for determining whether or not the normal fuel pressure in the IFB ECU, the IFB ECU 6 is basically to receive the current fuel pressure and fuel temperature from the fuel pressure sensor 4 and the fuel temperature sensor (5). .

When the fuel pressure and the fuel temperature are input as described above, the IFB ECU calculates the current fuel pressure according to the fuel composition and the saturated steam pressure at the fuel temperature, and then calculates the pressure margin according to the current fuel pressure and the fuel temperature.

Here, the saturated steam pressure and the pressure margin are the data embedded in the IFB ECU mapped according to the fuel pressure and the fuel temperature.

Subsequently, the IFB ECU compares the current fuel pressure with the sum of the saturated steam pressure and the pressure margin calculated as described above, where the fuel pressure is determined to be normal if the current fuel pressure is equal to or greater than the sum of the saturated steam pressure and the pressure margin. If it is lower than the sum of the pressure margins, it is determined that the fuel pressure is abnormal.

When the fuel pressure is determined to be normal as described above, the IFB ECU 6 transmits the normal state to the engine ECU 7 through CAN communication. Therefore, the engine ECU 7 performs misfire diagnosis only under normal pressure. The misfire diagnosis is prohibited under abnormal pressure.

In this way, according to the present invention, by prohibiting misfire diagnosis when the fuel pressure falls below the normal level, the problem of misdiagnosis due to engine misfire due to a vehicle abnormality in a simple low fuel level state can be solved. Diagnostic prohibition control can be implemented by simply adding logic by using pre-installed components without additional hardware.

As described above, according to the misfire diagnosis control method of the LPI engine according to the present invention, in order to solve the problem of misdiagnosis caused by the misfire of the engine due to a vehicle failure when the LPI system is in a low fuel level state, the vehicle is mounted on the vehicle. By monitoring the fuel pressure in real time using the sensors, and preventing the misfire diagnosis when the monitored current fuel pressure is lower than the normal level, the misdiagnosis is caused by the engine misfire due to the vehicle failure at the low fuel level. The problem can be solved.

In addition, the present invention has the advantage that unlike the gasoline vehicle, in the LPI system without the fuel level sensor can be implemented by simple logic addition by using the pre-installed components without additional hardware additional control of misfire diagnosis.

Claims (2)

Receiving, by the IFB ECU, the fuel pressure and the fuel temperature from a fuel pressure sensor and a fuel temperature sensor installed in the fuel line; Determining whether the fuel pressure is normal based on the current fuel pressure, fuel temperature, and fuel composition learning value received by the IFB ECU; The IFB ECU transmitting to the engine ECU whether the fuel pressure is normal; The engine ECU performing misfire diagnosis only when the fuel pressure is normal according to whether the fuel pressure is normal, and prohibiting misfire diagnosis when the fuel pressure is abnormal; True diagnosis control method of the LPI engine comprising a. The method according to claim 1, The IFB ECU determines whether the fuel pressure is normal, Calculating the saturated steam pressure at the current fuel pressure and the fuel temperature according to the fuel composition; Calculating a pressure margin according to the current fuel pressure and the fuel temperature; Comparing the current fuel pressure with the sum of the calculated saturated steam pressure and the pressure margin, if the current fuel pressure is more than the sum of the saturated steam pressure and the pressure margin, the fuel pressure is determined as normal, and if the fuel pressure is lower than the sum of the saturated steam pressure and the pressure margin, the fuel pressure is abnormal. Determining that; Misfire diagnosis control method of the LPI engine, characterized in that consisting of.

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