KR20000076448A - Control method - Google Patents

Abstract

The invention relates to an individually operable fuel injector 18 arranged to receive fuel from a common rail 17 while an associated engine is in operation, wherein each of the fuel injectors 18 is a control chamber 25. Control valves (29, 35) operable to control fuel pressure in the fuel cell, and the fuel exits the control chamber (25) and returns to the fuel reservoir (10). CLAIMS 1. A method of controlling fuel pressure in a common rail (17) or an accumulator, the method comprising: monitoring fuel pressure in a common rail (17); Controlling the fuel flow rate supplied to the common rail 17; And control valves 29, 35 of at least one fuel injector 18 where the fuel pressure of the common rail exceeds a predetermined threshold, where the control valves 29, 35 are at least one fuel injector 18. At least one fuel from the common rail 17 by actuating the fuel pressure in the control chamber 25 of the control chamber 25 and in such a manner as to ensure that fuel injection is not initiated through the one or the plurality of fuel injectors 18. Releasing fuel pressure in the common rail to flow through the control valves 29, 35 of the fuel injector 18 into the fuel reservoir 10.

Description

Control method {CONTROL METHOD}

The present invention relates to a control method for use in controlling the operation of a common rail or accumulator type fuel system for a compression ignition internal combustion engine. Specifically, the present invention relates to a control method used in the case of controlling fuel pressure in a common rail which is generally used.

In known common rail fuel systems, high pressure fuel pumps are used to fuel common rails or accumulators. The fuel pressure in the common rail is controlled by controlling the fuel flow rate supplied to the high pressure fuel pump using a suitable metering valve. The fuel limit valve can be used to prevent rail pressures exceeding preset thresholds for safety reasons.

Such a fuel system allows the engine to operate at a substantially constant speed for a constant load because of a uniform fuel demand and for the metering valve to supply fuel to the fuel pump at about the same speed as fuel is provided by the fuel injector. It works satisfactorily when it needs to be simply adjusted. However, if the engine does not operate in this way, the metering valve does not need to be adjusted to quickly and sufficiently compensate for changes in the fuel supply flow rate by the fuel injector, so that the rail pressure exceeds the desired fuel pressure by a considerable amount. Can be taken, and it may take a relatively long time to lower the fuel pressure if the only action taken to correct the fuel pressure is to reduce the fuel flow rate supplied to the common rail by the fuel pump.

U.S. Patent No. 5,711,274 discloses that after the engine is switched off, the rail pressure is released by applying a control pulse to the control valve of the fuel injector such that the fuel is returned to the fuel reservoir without injecting fuel into the engine's cylinder or combustion space. A method is disclosed. As a result, the provision of a separate pressure relief valve can be avoided.

European Patent No. 0,896,144 shows that while the coupling engine is in operation, it is sufficient for fuel to escape from the rail to the low pressure reservoir through the control valve, but for a period of time that is not sufficient to initiate fuel injection, In the case where injection is not desirable, a configuration is disclosed in which the rail pressure can be released by applying power to the control valve of one fuel injector.

It is an object of the present invention to provide a control method capable of controlling fuel pressure in a common rail or accumulator of a fuel system during use of an engine.

According to the present invention, an individually operable fuel injector arranged to receive fuel from a common rail while the coupling engine is in operation, wherein each fuel injector has a control valve operable to control fuel pressure in the control chamber, 1. A method of controlling fuel pressure in a common rail or accumulator of a fuel system having a fuel exiting a control room and returning to a fuel reservoir

Monitoring fuel pressure in the common rail;

Controlling the fuel flow rate supplied to the common rail; And

Control valve of at least one fuel injector when the fuel pressure of the common rail exceeds a predetermined threshold, wherein the control valve is arranged to control the fuel pressure in the fuel chamber of the at least one fuel injector and the one or the plurality of fuel injectors Releasing fuel pressure in the common rail such that the fuel flows from the common rail through the control valve of the at least one fuel injector to the fuel reservoir via the control valve of the at least one fuel injector. A fuel pressure control method is provided.

This configuration is advantageous when the rail pressure is significantly greater than the predetermined pressure, and the rail pressure drops by simply limiting the amount of fuel supplied to the common rail and by waiting for a natural leak of the system to reduce the pressure. It can be seen that the rail pressure can be released quickly rather than waiting.

It is preferable that a calibration operation is determined during the period of the maximum control pulse that can be applied to each of the fuel injectors without generating fuel injection prior to the control method. The correction operation involves using at least one engine mounted accelerometer, the signal output of which is filtered in a manner that detects needle movement for each fuel injector. If desired, the correction operation can be repeated from time to time.

The common rail may be provided with a separate pressure limiting valve for use when the fuel pressure is dangerously high.

Preferably, when the control valve is operated to release the rail pressure, the operation of the control valve can be made using a relatively low voltage (eg battery voltage). As a result, the control valve can be operated repeatedly in a short time, so that a relatively large amount of fuel can be returned to the fuel reservoir. Another advantage of using a low power source is that the current applied to the control valve is relatively low, resulting in less heat generation. The use of a lower voltage is advantageous in the repetitive operation of the control valve, but it is possible to perform the repetitive operation of the control valve using a higher voltage.

When a plurality of control valves are operated to release fuel pressure of the common rail, the control valves are easily operated continuously.

The fuel flow rate supplied to the common rail can be controlled using a metering valve to control the fuel supply flow rate to the high pressure pump. Alternatively, a variable displacement fuel pump can be used to fuel the common rail.

The invention will be described in an embodiment manner with reference to the accompanying drawings.

1 illustrates a fuel system that can be controlled according to a control method according to the invention.

2 is an illustration of a fuel injector suitable for use in the fuel system of FIG.

1 is a diagram illustrating a fuel system that can be controlled according to the control method of the present invention, and FIG. 2 is a diagram showing a fuel injector suitable for use in the fuel system of FIG.

1 illustrates a fuel system for use in an internal combustion engine, which is connected to a metering valve 13 provided at the inlet of the high pressure fuel pump 14 through a low pressure pump 11 and a filter 12. A fuel reservoir or fuel tank 1 for storing the fuel to be supplied is included. The metering valve 13 is conventional and electrically controlled by the controller 15 via the control line 16. The high pressure fuel pump 14 includes a high pressure outlet in communication with the inlet of the common rail 17. The common rail 17 is connected to a plurality of individually injectable fuel injectors 18. Each of the plurality of injectors 18 is arranged to provide fuel to each cylinder of the combined compression ignition internal combustion engine.

The common rail 17 is provided with a mechanical pressure limiting valve 19. The pressure limiting valve 19 operates when the fuel pressure in the common rail 17 exceeds the maximum threshold, and the pressure limiting valve 19 then opens to limit the pressure in the common rail 17. As a result, the fuel exiting from the common rail 17 through the fuel restriction valve 19 is returned to the fuel reservoir 10. The fuel limit valve 19 acts as a safety valve and prevents dangerously high pressures from being applied to the common rail 17.

A controller 15 is connected to the plurality of sensors 20, the outputs of which indicate engine operating conditions. As illustrated in FIG. 1, the sensors 20 each comprise a pressure sensor 20a arranged to monitor fuel pressure in the common rail 17. The sensors 20 indicating the air temperature and pressure applied to the cylinder of the engine also include an engine speed and position sensor and an accelerometer that can be used to detect the onset of fuel ignition or the onset of fuel injection. can do.

2 illustrates a fuel injector suitable for use with the fuel system of FIG. 1. The fuel injector illustrated in FIG. 2 includes a valve needle 21 that can move slowly inside a bore formed in the nozzle body 22. The valve needle 21 may be fastened to a seating controlling the fuel supplied by the fuel injector to the ignition space of the coupling engine. The bore in which the valve needle 21 slides is in communication with a fuel supply passage 23 in communication with the common rail 17 in use. The fuel supply passage 23 may include an end region of the valve needle 21, a portion of a bore in the fuel supply passage 23 through which the valve needle 21 may be repelled, and a first distance piece 30. It communicates with a control chamber 25 defined by the surface through a small diameter drill, and inside the fuel supply passage 23 a spring 26, where the spring 26 is directed toward the magnetic seating. Is arranged to apply a force on the valve needle 21 to the valve needle 21. The control chamber 25 is connected to the chamber 28 and the second distance piece defined by the first distance piece 30 through a small diameter hole 27 provided in the first distance piece 30. It is in communication with the recess provided by the recess.

A tabular valve member 29 may move within the bore provided in the second distance piece, and the lower end of the tubular valve member 29 engages with the surface of the first distance piece 30. A backleak or return passage 33 (illustrated in FIG. 1) in communication with the fuel reservoir 10 by engaging the tubular valve member 29 and the first distance piece 30. And communication between the chamber 28 and the chamber 31 in communication with the perforations 32 is controlled.

A portion of the valve member 29 disposed in the chamber 31 is movable armature under a magnetic field generated by an electromagnetic actuator 35 operable under the control of the controller 15. move the armature; The actuator 35 includes a spring that urges the valve member 29 for engagement with the first distance piece 30, and when the actuator 35 is not powered, the chamber 28 may be Not in communication with the fuel reservoir 10. As a result, fuel cannot escape from the control chamber 25, and since the control chamber 25 communicates with the supply passage 23, the fuel in the control chamber 25 may cause the valve needle 21 to self seat. When tightened, a large force is applied to the valve needle 21 supporting the spring 26 so that fuel injection does not occur.

In use, when injection is initiated, the actuator 35 is energized to lift the valve member 29 away from the first distance piece 30. As a result, fuel can escape from the control chamber 25 into the chamber 28 and into the chamber 31 along a passage defined by the valve member. The chamber 31 is in communication with the fuel reservoir 10 as discussed so far, so that the fuel exiting from the control chamber 25 is returned to the fuel reservoir 10. The operation of the actuator 35 causes the fuel pressure in the control chamber 25 to drop, and the fuel flow rate that can flow from the passage 23 to the control chamber 25 is limited by the small diameter bores 24. Will be understood. The magnitude of the force that forces the valve needle 21 toward its seating is thus reduced, and the fuel pressure from its seating forces the surface of the valve needle 21 acting on a properly oriented thrust surface. A predetermined point is reached above which the valve needle 21 can be lifted off. Thus the infusion is initiated.

When the injection is complete, the actuator 35 is powered off and the valve member 29 is returned for engagement with the first distance piece 30 under the action of the actuator 35 spring. As a result, fuel is no longer able to exit from the control chamber 25 into the fuel reservoir 10, and continued communication between the control chamber 25 and the passageway 23 causes the fuel pressure in the control chamber 25 to decrease. Is increased. The increased fuel pressure in the control chamber 25 increases the magnitude of the force applied to the valve needle 21 to urge the valve needle 21 toward its seating, and the valve needle to engage in its seating. The point beyond (21) is returned is reached and the injection ends.

Having briefly described the operation of the fuel injector illustrated in FIG. 2, the operation of the fuel system of FIG. 1 is described.

Fuel is supplied to the fuel pump 14 at a predetermined flow rate regulated by the metering valve 13, and the setting of the metering valve 13 is selected in response to various control signals applied to the controller 15. Fuel is supplied from the high pressure fuel pump 14 to the common rail 17. Supplying fuel to the common rail 17 at a flow rate substantially equal to that provided by the fuel injector 18 to maintain the common rail 17 at a substantially constant fuel pressure, and thus the metering valve 13 Is preferably controlled. However, maintaining the fuel pressure in the common rail 17 at a substantially uniform level by simply changing the amount of fuel supplied to the pump 14 through the metering valve 13 at the time of use is the fuel supplied to the engine. It is known that a significant time may be delayed between the time when the flow rate begins to decrease and correspondingly the time when the fuel flow rate supplied to the high pressure pump 14 is reduced, which is not necessarily satisfactory. As a result, the fuel pressure in the common rail may rise above a predetermined level.

According to the present invention, when the fuel pressure in the common rail 17 is closed to a predetermined level, the metering valve 13 is used to control the fuel flow rate in which the rail pressure is supplied to the common rail 17. Controlled. Detecting the case where the fuel pressure in the common rail 17 rises above a predetermined level, the actuator 35 of the fuel injector 18, which is not used to supply fuel to the combustion engine at a given moment, is powered on. The valve member 29 is then lifted away from the first distance piece 30. As a result, the fuel can escape from the control chamber 25 of the fuel injector 18. The application of power to the actuator 35 takes place in a sufficiently short period of time that the fuel pressure in each of the control chambers 25 does not drop to a level low enough to enable the movement of the coupling valve needle 21. Therefore, the power supply of the actuator 35 allows the fuel to escape from the control chamber 25 of the fuel injector 18, but the fuel is injected into the cylinder of the associated engine through the fuel injector 18. It will be understood that this does not occur.

In each case, after releasing the power of the actuator 35, the flow of fuel continued through the drilling part 24 applies pressure to the control chamber 25 again. Obviously, the application of power to the actuator allows fuel to flow from the control chamber 25 to the low pressure fuel reservoir 10, since the control chamber 25 is supplied with fuel from the common rail 17, It will be appreciated that powering up and releasing the actuator 35 makes it possible to release the fuel pressure in the common rail 17 without generating fuel injection.

The operation of powering on and powering off the actuator of the fuel injector not used for fueling is repeated until the common rail pressure drops to a suitable level, after which the rail pressure is controlled using the metering valve.

The predetermined fuel pressure level may be a fixed level or may vary depending on engine operating conditions (eg, engine speed and load). Likewise, thresholds beyond those used for the fuel injector to release the common rail pressure may be fixed or may vary depending on engine operating conditions.

The actuator 35 of the fuel injector 18 may be powered using a low voltage (eg, 12V battery voltage) when powering the actuator 35 is used to release the common rail fuel pressure. It can be seen that. Since a low battery voltage is used for powering the actuator 35, the actuator 35 generates a significant amount of fuel from the common rail 17 without generating significant heat levels in the fuel injector 18. Power may be repeatedly applied to the fuel reservoir 10 in a short period of time so as to exit the fuel reservoir 10. The selected actuator is easily powered up at a sufficiently high rate that several power-up operations may occur during the time that the other fuel injector completes one injection cycle. This operation can be difficult to achieve when high voltages are used.

Prior to use, it can be seen that a correction operation is performed to determine the maximum drive pulse interval that can be applied to each actuator 35 without generating fuel injection. Such measurements may include detection of the onset of combustion using an accelerometer, in-cylinder pressure sensor or fuel injector movement sensor. Clearly, this information is known for each of the fuel injectors, so that during subsequent use of the fuel system, if the fuel pressure in the common rail is repeatedly powered on and off the actuators of the various fuel injectors, the fuel injector Each actuator can be controlled in a manner that ensures that no fuel injection occurs. If desired, the correction operation may be repeated from time to time, for example during maintenance or maintenance of the fuel system. However, it will be appreciated that the correction operation may be omitted if desired.

The fuel system described so far can be modified in various ways. For example, the fuel injector need not be of the type described so far, and if desired, the control valve is configured to control the communication between the supply passageway and the control chamber, where the control chamber is always in communication with the fuel reservoir. Can be.

According to the present invention it is possible to provide a control method capable of controlling fuel pressure in a common rail or accumulator of a fuel system during use of an engine.

Claims (12)

Individually operable fuel injectors 18 arranged to receive fuel from a common rail 17 while the associated engine is in operation, wherein each of the fuel injectors 18 is a control chamber; a control valve (29, 35) operable to control fuel pressure in the chamber (25), the fuel exiting the control chamber (25) and returned to a fuel reservoir (10); In a method for controlling fuel pressure in a common rail 17 or accumulator of a fuel system, a) monitoring fuel pressure in the common rail (17); b) controlling the fuel flow rate supplied to the common rail 17; And c) at least one control valve 29, 35 of the fuel injector 18, where the fuel pressure of the common rail exceeds a predetermined threshold, wherein the control valve 29, 35 is configured to control the at least one fuel. Is arranged to control the fuel pressure in the control chamber 25 of the injector 18 and ensures that no injection of fuel is initiated through the one or more fuel injectors 18. Relieving the fuel pressure of the common rail to flow from 17 through the control valves 29, 35 of the at least one fuel injector 18 to the fuel reservoir 10. Fuel pressure control method comprising a. The method of claim 1, Fuel pressure control method in which the common rail (17) is provided to a separate pressure limiting valve (19). The method according to claim 1 or 2, And when the control valve (29, 35) is operated to release the rail pressure, the operation of the control valve (29, 35) is made using a relatively low voltage. The method of claim 3, And said relatively low voltage is a battery voltage. The method according to any one of claims 1 to 4, At least one control valve (29, 35) is repeatedly operated in a short time when the rail pressure is released. The method of claim 5, At least one control valve (29, 35) is operated several times during the injection cycle of another fuel injector (18). The method according to any one of claims 1 to 6, And when the rail pressure is released, a plurality of control valves (29, 35) are operated to release fuel pressure of the common rail. The method of claim 7, wherein Fuel pressure control method in which the control valve (29, 35) is operated continuously. The method according to any one of claims 1 to 8, The fuel pressure control method in which the fuel flow rate supplied to the common rail (17) is controlled using a metering valve (13) to control the fuel supply flow rate to the high pressure pump (14). The method according to any one of claims 1 to 8, A method of controlling fuel pressure, wherein a variable displacement fuel pump is used to supply the common rail. The method according to any one of claims 1 to 10, And a calibration operation determined during a period of maximum control pulse that can be applied to the control valves (29, 35) of each of the fuel injectors (18) without generating fuel injection. The method of claim 11, The correcting operation includes using at least one engine mounted accelerometer, the signal output of which is filtered in a manner to detect needle movement for each fuel injector.