KR20100014658A - Method for the diagnosis of a shut-off valve - Google Patents

Abstract

The invention relates to a method for the diagnosis of a shut-off valve (400, 500, 510) in a fuel line (50), wherein the shut-off valve is disposed in the fuel line between at least one reservoir and at least one injection valve (70), wherein the shut-off valve is closed for the diagnosis, and fuel is removed via an injection valve for the operation of an internal combustion engine. The shut-off effect of the shut-off valves is determined to be insufficient if the pressure in the fuel line does not drop in an unexpected manner.

Description

Diagnosis of shut off valves {METHOD FOR THE DIAGNOSIS OF A SHUT-OFF VALVE}

The present invention relates to a method of diagnosis and a fuel supply system of a shut off valve in a fuel line according to the type of independent claim.

Systems by compressed gas, so-called CNG (compressed natural gas) systems, typically include a series connection of an overpressure valve, a pressure regulation module, a pressure regulator shut off valve, a reservoir shut off valve in a low pressure system. In this case, the pressure regulating module itself usually also has a valve function that isolates the low pressure region from the high pressure region at too high a pressure, to prevent the injection valve or the injection valve from opening too reliably at too high pressure. will be.

The legal requirements define in particular the reservoir shut-off valve. However, the error of the shut off function, i.e. internal leakage, does not affect the normal operation of the vehicle. If the shut off devices are inadequately closed in the event of a failure, there is a risk that the entire contents of the reservoir may leak to the surroundings. It is therefore particularly important that the shut off action of the shut off device and valves is preferably checked regularly, preferably in advance, and a warning or error response is introduced in the event of a lack of shut off action.

DE 10 2005 048 456, which has not yet been published, describes how low fuel pressure is set downstream of the shutoff valve and how the fuel pressure increases downstream of the shutoff valve when the shutoff valve and the injection valve are closed. It is already described. Increasing fuel pressure is indicative of insufficient shut off action of the shut off valve.

In US 6,427,670 B2 a CNG system is known, for example, in which fuel is stored in a reservoir under pressure and supplied to the injection valve by a fuel line. After stopping the engine and closing the reservoir valve, it is provided to check the fuel pressure in the fuel line, and if the fuel pressure drops faster than expected, an external leak, i.e. a sealing leak of the fuel system to the external environment, It is recognized.

In contrast, the method according to the invention comprising the features of the independent claims claiming that the shut off action, ie the internal leakage of the shut off valve, which is arranged in the fuel line between the at least one reservoir and the at least one injection valve, is typically already present. There is an advantage that it can be inspected in less steps by means of sensors or measuring means. For this purpose the shut off valve is closed, the fuel pressure is monitored downstream of the closed shut off valve and the fuel continues to flow into the combustion chamber through an injection valve for engine operation. The expected fuel pressure is detected downstream of the shut off valve from the injected fuel mass, and the shut off action of the valve is insufficient if this fuel pressure does not deviate or decrease as expected from the expected fuel pressure downstream of the shut off valve. It is recognized.

Also preferred is a fuel supply system comprising the features of the independent claim claiming a device in the same manner. In this case, there is provided a controller having an adjusting means and a monitoring means, the apparatus means and a controller for carrying out the method according to the invention.

By means described in the dependent claims, further preferred embodiments and refinements of the method described in the independent claims are possible.

The shut off action is also recognized as insufficient if the fuel pressure exceeds the expected fuel pressure downstream of the shut off valve and / or the fuel pressure deviates from the expected pressure curve.

In a further preferred embodiment, the diagnosis of the shut off valve is carried out at the stop of the engine and the engine is operated until the end of the diagnosis.

It is also advantageous to take into account the variables characterizing the temperature of the fuel when measuring the pressure in the fuel line.

Fuel mass in the system can be detected in this preferred manner from pressure and temperature, and the shut off action of the valve is considered insufficient when the fuel mass in the fuel line does not decrease below the expected fuel pressure downstream of the shut off valve. Can be.

1 is a view showing an embodiment of a fuel supply system according to the present invention.

1 schematically shows a fuel supply system for operating an engine with liquefied gas or compressed gas, for example hydrogen or natural gas. Fuel is stored under pressure in the first reservoir and the second reservoir 100, 110 in the illustrated embodiment. The pressure of the fuel present in the first reservoir and the second reservoir 100, 110, and indirectly the fuel level, is indirectly applied to the first reservoir pressure sensor and the second reservoir pressure sensor 200, 210, respectively. Is monitored by. The two reservoirs 100, 110 are connected by a common fuel line 50, which supplies fuel to the pressure regulating valve 300 and is located 4 downstream of the pressure regulating valve 300. To two injection valves 700. One reservoir shut-off valve 500 and 510 is disposed between the common fuel line 50 and the reservoirs 100 and 110, respectively. A shut off valve 400 is provided upstream of the pressure regulator 300, and a third pressure sensor 220 is provided between the pressure regulator 300 and the shut off valve 400, and the pressure regulator 300 and the injection valve 700. Between the fourth pressure sensor 230 is provided. A filling nozzle 600 is disposed at the end of the common fuel line 50 for filling the fuel system.

In normal operation of the fuel supply system, for example, hydrogen is stored under pressure of up to 300 bar in the two reservoirs 100, 110. The reservoir shut off valves 500, 510 and the shut off valve 400 in the fuel line 50 are open. In this case a reservoir pressure of, for example, less than 300 bar appears in the common fuel line 50 up to the pressure regulator and is measured by the third pressure sensor 220. Since the pressure regulator 300 reduces the pressure applied, downstream of the pressure regulating valve 300, for example, two to six bar pressure is applied in the fuel line. At this low pressure fuel is injected by injection valve 700 into the combustion chamber of an engine, not shown.

It is provided to close the shut off valves 400, 500, 510 in case of failure or under special operating conditions. For example, if there is a leak in the injection valve 700 or the fuel line, the fuel is prevented from leaking to the surroundings. Since shut off valves are closely related to safety, it is desirable to regularly check the shut off action of shut off valves.

In order to check the sealing force or shut off action of the shut off valve, it is provided according to the invention to close the shut off valve 400 and to monitor the fuel pressure downstream of the shut off valve 400, the injection valve 700 being provided. ) Continues to run for engine operation.

The fuel mass entering the combustion chamber is detected from known operating conditions, such as the pressure in the fuel line and optionally temperature, and the injection duration of the injection valve 700. The injected fuel mass reduces the fuel mass in the fuel line and causes a pressure drop in the fuel line when the shut off valve 400 is closed to seal close. If the pressure drop does not occur in the expected manner, it can be seen that the fuel is subsequently perfused into the fuel line through the shut off valve.

The fuel pressure expected in the fuel line by each injection process is also reduced downstream of the closed shut off valve. As a result, the number of injection procedures increases, thereby increasing the pressure difference between the downstream side and the upstream side of the shut off valve.

Thus, it is also possible according to the invention to monitor the differential pressure on the shut off valve.

It is also possible to set a threshold above the expected fuel pressure, at which threshold the shutoff action of the shut off valve 400 is still sufficient. The threshold can be updated corresponding to the fuel mass flowing out through the injection valve.

The pressure may be checked using a fourth pressure sensor 230 downstream of the pressure regulator to further improve the accuracy of the inspection of the shut off action. To this end the pressure can be lowered to a pressure below the pressure regulation threshold through the discharge of fuel by the injection valve 700 downstream of the closed shut off valve 400 to be inspected. If the pressure regulation threshold of the pressure regulator 300 is located at 6 bar, for example, the pressure will be adjusted below 6 bar, ie 2 bar. Under these conditions the pressure regulator 300 is fully open and the pressure sensor 230 directly measures the pressure downstream of the shut off valve 400. This procedure is advantageous in that the differential pressure at the shut-off valve 400 is increased on the one hand and on the other hand the third pressure sensor in the high pressure region due to the smaller measurement region of the fourth pressure sensor 230 in the low pressure region. There is an advantage that more sensitive than 220. This increases the accuracy and reliability of the measurement. In order to improve the accuracy, the mass increase in the monitored volume can be accurately calculated through further temperature measurements. The temperature measurement can be made by a temperature sensor in the monitored volume or by a reservoir temperature sensor.

Of course, other embodiments of the fuel supply system according to the invention can also be considered. As such, for example, the first pressure sensor and the second pressure sensor 200, 210 may be omitted, and the fuel pressure may be detected in another type and manner or for example by the third pressure sensor 220. have.

It is also possible to operate only one fuel reservoir or two or more fuel reservoirs.

In addition, the method according to the invention is not limited to the diagnosis of the shut off valve 400. In particular, the shut off action can also be diagnosed in the two reservoir valves 500, 510.

If the diagnosis is carried out, for example at high loads, there is a risk that the fuel pressure decreases to a large slope below the critical pressure downstream of the closed shut off valve, so that engine operation is no longer possible. To prevent this, a pressure threshold or a load threshold is provided in a suitable manner, and no diagnosis is carried out below this pressure threshold and the load threshold.

If the load demand is small, the shut off valve closes until the fuel pressure drops noticeably downstream of the shut off valve. This enables further operation of the engine and the conduct of diagnostics. While the shut off valve is closed, the injected fuel mass accumulates and compares with the maximum defined for the shut off valve, at which pressure drop can be noticed.

The defined permissible maximum value of the accumulated injection fuel mass can for example be detected in advance and optionally stored in the property field for the call. If the stored permissible maximum value is exceeded, it is recognized that there is an error in the shut off valve.

Alternatively a suitable maximum allowable opening time of the shut off valve can also be stored. It is also possible to provide a second pressure threshold, above which the shut off valve can be closed again. It is also possible to operate the shut off valve periodically.

In addition, the shut off action of the shut off valve that is recognized as insufficient may be stored in the error memory.

It is also possible to carry out the diagnosis at set intervals or at prescribed times. In this case, the shut off action may only be perceived as insufficient, for example, if confirmed in a plurality of diagnoses.

In addition, further diagnostics during the leak diagnosis can be carried out, in particular electrical diagnostics of the shut off valve, such as, for example, the diagnosis of a line interruption or of a short circuit depending on the supply voltage. This procedure makes it possible to distinguish between the final stage and the components (valve) in a simple type and manner.

Claims (6)

Shut-off valves 400, 500, 510 are disposed in fuel line 50 between one or more reservoirs 100, 110 and one or more injection valves 70, Fuel pressure is measured downstream of shut off valves 400, 500, 510, Fuel enters the combustion chamber through the injection valve, Shut off valves 400, 500, 510 are closed for diagnostic purposes, In the diagnostic method of the shut off valves 400, 500, 510 in the fuel line 50, The fuel mass introduced through the injection valve is detected, The fuel pressure expected downstream is detected from the introduced fuel mass, In the fuel line, characterized in that the shut off action of the shut off valves 400, 500, 510 is perceived as insufficient if the fuel pressure deviates from the expected fuel pressure downstream of the shut off valves 400, 500, 510. Diagnostic method of shut-off valves. The pressure off curve of claim 1 wherein the shut off action of the shut off valves 400, 500, 510 is such that the fuel pressure exceeds and / or expected the fuel pressure expected downstream of the shut off valves 400, 500, 510. A method of diagnosing a shut off valve in a fuel line, which is perceived as inadequate when out of range. Method according to one of the preceding claims, wherein the shut off valve (400, 500, 510) is closed upon engine stop and the engine is operated until the diagnosis is complete. 4. A method according to any one of the preceding claims, wherein a variable characterizing the temperature of the fuel is taken into account when measuring the pressure in the fuel line (50). The fuel mass in the fuel line 50 is detected from the pressure and the temperature, and the fuel mass in the fuel line 50 does not decrease correspondingly to the introduced fuel mass. A method for diagnosing shut off valves in a fuel line, wherein the shut off action of the shut off valves 400, 500, 510 is perceived as insufficient. In a fuel supply system having one or more reservoirs 100, 110, injection valves 70, shut off valves 400, 500, 510, and a controller, The controller for diagnosing the shut off valves 400, 500, 510 comprises an adjusting means and a monitoring means, the regulating means comprising an adjustment means for the diagnosis of the shut off valves 400, 500, 510. , 500, 510 are formed in such a way that The monitoring means are installed in such a way as to monitor the fuel pressure downstream of the shut off valves 400, 500 and 510 and to detect the expected fuel pressure according to the fuel mass flowing into the combustion chamber through the injection valve, Insufficient shut off action of the shut off valve (400, 500, 510) is recognized when the fuel pressure exceeds the expected fuel pressure downstream of the shut off valve (400, 500, 510).

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