EP0666416B1 - Fuel injection device for internal combustion engines, in particular for a diesel engine, as well as a method for monitoring this device - Google Patents

Abstract

The injection quantity of the fuel into the combustion cylinders is determined by a quantity controlled feed device (120). The quantity controlled feed device is formed as a flow regulator connected ahead of the fuel pump (6), which has a throttle valve operable from a control appts. (31) with or without position feed-back or a timed closure valve. For the throttle valve of the flow regulator a series-arranged pressure correction throttle valve, which alters the pressure drop over the throttle valve, so that after the flow regulator the required theoretical pressure always exists.

Description

The invention relates to a fuel injection system for an internal combustion engine, especially for a diesel engine, with for each combustion cylinder at least one controlled by a control unit Injection element, which has a closable injection opening leading into the cylinder and has a pressure space arranged in front of the latter, the one with a fuel pump depending on engine speed, Load and load change is connected to the high pressure part; and a method for monitoring the fuel injection system.

In a known fuel injection system according to CH-A5 668 621 becomes the injection quantity for a given opening cross section of the injection opening primarily through the one in front of the opening valve Fuel pressure determined. It becomes constant or through change the pressure corresponding to that determined in a control unit Pressure maps supplied variable to a certain extent. Disadvantageous here is that the injection amount is due to wear or clogging of an opening cross section changed approximately linearly and thus influencing the resulting engine torque. This is from the Injection system as little detectable as cracks in the Area of the injection opening or a break of a nozzle tip. in the there are further shortcomings in this known injection system if there is an excessive amount of leak oil, e.g. in the event of a line break. In such cases, large quantities can go undetected into the environment escape. Damage to the nozzle tip or other malfunctions of the injection valves can with this conventional injection system may not be recognized and endanger users. There is also the problem with large-volume diesel engines that used abrasive, but very inexpensive heavy oil for Control of the injection elements is used. In practice it has pointed out that this heavy oil works properly these injection elements are not guaranteed over a longer period of time is.

GB-A-2 246 175 is now another Injection system known, in which the injection quantity is dosed via a pump. The is through the Injectors self-used amount of fuel back in the pump suction area, i.e. downstream, the Quantity metering device returned. I.e. the needed amount of fuel delivered remains in the supply area of the Injectors back and actually gets in the combustion chamber. Furthermore, this has quantitative Delivery the advantage of a leak in this Supply area the fuel amount is not easy up is increased to the maximum pump output, but remains constant according to the characteristic values. By the Pressure drop caused by such a leak can also this disorder can be found at all. At the in However, the solution shown in this document proves to be the execution of the return to the cylinder space as disadvantageous because in the area of the pump itself a large one Leakage must be accepted, which also must be returned, and an undesirable Heating of the fuel and a loss of performance leads. Such an injection system is also in the controllability and adjustability of the pump relative set narrow limits.

The object of the present invention was now a such injector with quantity metering further to improve in order to avoid the disadvantages mentioned and thus heating the fuel and the resulting to reduce the resulting performance losses.

According to the invention, this object is achieved by a Fuel injection system with the features of claim 1 solved.

Further, preferred embodiments of the invention result themselves from the dependent claims 2 to 8.

According to the method according to the Claims 9 and 10 for monitoring a

Fuel injection systems according to claims 1 to 8 suggested.

The quantity is advantageously metered in using a known one Current regulator or a 2/2-way valve, which depends on the piston position a fuel pump provided as a radial piston pump opens or closes.

In a preferred embodiment, a connected in parallel to the fuel pump and into the high pressure section leading line provided with a check valve, with which a venting or a pressure build-up of the high pressure part made possible by the preferably electrically operated pre-feed pump is. This gives the major advantage over the known diesel engines, that the high pressure part is emptied at a service or the like can be brought back to a certain pressure very quickly can, while in conventional diesel engines this by means of High pressure pump has to be run, which is very time consuming because this pump in relation to that formed by the high pressure part Volume can only convey small quantities.

The pressure accumulator and the high pressure lines of the are advantageous High-pressure part of a tubular, forming an annular gap Enclosed envelope, which opens into the fuel tank, whereby at Leakages in this high-pressure part fuel losses and resulting Pollution can be avoided.

Furthermore, in the case of large-volume internal combustion engines, for example in ship or stationary power generation drives that with Heavy fuel oil work, the injection elements a fuel pump with a quantity metering of heavy oil and a separate high pressure pump with or without quantity metering for the control of the injection elements be assigned, the high pressure pump for the Control circuit approximately corresponds to the fuel pump, advantageously generates a slightly higher pressure. By using it a separate medium for the control of the injection element this can be operated without problems, while in known systems, at which use abrasive fuel for this, on the one hand when starting then difficulties arise when this is still cold and therefore very bad is viscous, and secondly this fuel wears out quickly the highly sensitive control elements and also blockages brings about the same.

Fig.1

eine schematische Darstellung einer erfindungsgemässen Einspritzanlage eines Dieselmotors,

Fig.2

eine schematische Darstellung einer Mengendosiereinrichtung, einer nachfolgenden Kraftstoffpumpe sowie eines Einspritzelementes jeweils im Halbschnitt,

Fig.3

ein hydraulisches Schema einer als Stromregler ausgebildeten Mengendosiereinrichtung.

Exemplary embodiments of the invention and further advantages thereof are explained in more detail below with reference to the drawing. It shows:

Fig. 1

1 shows a schematic representation of an injection system of a diesel engine according to the invention,

Fig. 2

1 shows a schematic illustration of a quantity metering device, a subsequent fuel pump and an injection element, each in half section,

Fig. 3

a hydraulic diagram of a metering device designed as a current regulator.

1 shows a fuel injection system 30 for an internal combustion engine provided diesel engine 1 of a motor vehicle, the several Combustion cylinder 110, one of which together are known and therefore not described in detail below Crank mechanism 112 for the piston 114 is illustrated. For each combustion cylinder 110 there is an injection element 2 and one Intake and discharge valve arrangement 103, 102 are provided. Here too as with all that is conventional in this system, not everybody is Explained in detail. Furthermore, there is one in this internal combustion engine Fuel supply device 3, a central control unit 31 and a battery 84 that supplies this electrically.

With the central control unit 31, the diesel engine 1 is made to measure the accelerator pedal 75 operated by a driver and others, not closer Controls shown controlled. For this purpose it is on known way as a controller 83 for the solenoid valves 60 of the Injection elements 2, as control 82 of the fuel pump 6 and for others also not shown receiver effective. Processed for this in addition to the accelerator pedal signal, it is primarily the position signal or signals 76 as well as further signals 32 of the fuel pressure necessary for fine corrections in the high pressure section 9, signals 79, 80, 81, 85 for the air, pressure and temperature conditions before combustion or in the exhaust gas state. The signals can be processed digitally or analog.

The fuel supply device 3 comprises a fuel tank 34, a line 12 extending from this, a prefeed pump 243, one Fine filter 89 and a fuel pump 6, which the fuel with High pressure from 200 to 2000 bar via a check valve 6 'and one Line 9 'in the high pressure part 9 having a chamber 9 "promotes. This high-pressure part 9 is included in each injection element 2 Pressure chamber 13 connected, which immediately before one in the cylinder 110 leading injection opening, which can be closed by a valve body 15 4 is arranged. The line 9 'is also over for safety a pressure relief valve 7 is connected to the fuel tank 34. The Fuel pump 6, which supplies a plurality of injection elements 2, is from Control unit 31 is controlled in such a way that, depending on the engine speed, Load and load change works, taking the fuel high speed and high load with usually a high pressure, meanwhile at low load and low speed to a small pressure pumps.

The amount of fuel injected in the combustion cylinder is by means of a quantity metering device operated by the control unit feedable. This quantity metering device is included designed as a current regulator 8 connected upstream of the high pressure pump 6, which is a throttle valve which can be actuated by the control unit with or without Position feedback of the valve body or a clocked closing valve having. To achieve a constant pressure difference in the metering valve can this a pressure correction throttle valve connected in series be assigned, which is described in detail below for FIG. 3.

The fuel pump 6 supplies a quantity of fuel that is the number the injection elements fed by it and the desired injection quantity adapted, and it also supplies an additional amount of fuel, which is for a pressure change in the entire line system communicating with it is necessary because primarily with a rapid change in fuel pressure the pump delivery rate deviates from the average injection rate considerably. This is necessary because of changes in state an additional amount is required as the injection pressure changes. The injection duration of the fuel determined by the control unit 31 into the Cylinder and the dimensioning of the injection quantity at the quantity metering device must be coordinated. The control unit 31 is designed in such a way that, with it, that of the Quantity metering device generated injection quantity together with the programmed activation time of the injection valves exactly the desired Injection pressure result, so that always an optimal fuel supply takes place. This means if the from the injectors and their leakage to the amount determined by the current regulator agree, this for an injection pressure deviating from the target pressure leads. The less reliable actuator, usually one of the Injection elements 2, for example, by means of known rotational uniformity detection be determined and receives depending on the severity the deviation a corrected actuation period or is switched off. In the latter case is then a correction to that of the current controller controlled amount necessary. When dimensioning the injection quantity an additional delivery rate may have to be supplied per injection the temperature and pressure dependent leakage behavior corresponds to the system. However, if that comes from the control of the injection element resulting leakage amount as well as the plant leakage currents According to the invention via a leak oil collection line 33 between the Quantity metering device and the fuel pump is returned such an additional output is not necessary. Then it is unique an additional quantity for pressure changes in the entire high pressure system to consider.

Furthermore, one is from the prefeed pump 243 to the fuel pump 6 connected in parallel and leading into the high pressure part 9, provided with a check valve 42 line 12 'provided with which a ventilation or a pressure build-up of the high pressure part 9 by the preferably electrically operated pre-feed pump 243 enables is. Furthermore, the pressure accumulator 9 "and the high pressure lines 9 'of the High-pressure part 9 of a tubular, an annular gap 91 ' enclosing sheath 91, which opens into the fuel tank 34. Leakages from this high-pressure part can be collected as a result and in addition, these can be Detect the monitoring device immediately.

2 illustrates an injection element 2, one which supplies it Fuel pump 6, which is connected upstream of a quantity metering device 120 is controlled by the control unit 31 and via one of the fuel tank 34 outgoing line 12 by means of the prefeed pump 243 Fuel is fed. A pressure control valve connected in parallel to the latter 135 ensures a constant supply pressure of the in the Quantity metering device 120 guided fuel.

This quantity metering device 120 has a 2/2-way valve 39, which to achieve the desired fuel injection quantity depending the position of the pump piston 41 of the fuel pump 6 opens or closes. This is preferably done via connecting lines 82 connected to the control unit 31 valve 39 in the upper position of the Piston 41 opened until it e.g. by the position of the crank mechanism 112 defined stroke has been moved in the suction direction and the suctioned quantity corresponds to the target specification. This allows a volumetrically defined, very precise injection quantity in a simple manner produce. The fuel reaches a from the valve opening 39 ' Chamber 35 and from there via a check valve 36 into the fuel pump 6. In this chamber 35 also leads Leakage oil line 33, into which the leakage currents from the injection element 2 and from the system, which flow back from a line 10. A check valve 37 between the chamber 35 and the drain line 33 causes that with valve 39 open due to the increasing pressure Connection to the leak oil collection line 33 is temporarily interrupted. As soon as the valve 39 is closed and the fuel pump 6 after as before, the pressure in the chamber 35 is reduced considerably and the check valve 37 opens and jammed leak oil in the line 33 is thereby also sucked in and subsequently into the high pressure part 9 promoted. This arrangement results in a closed one Circulation of the leakage oil as a whole and it is therefore not the control unit 31 Enter size for an additional delivery quantity. Therefore affect different leakage quantities of the injection elements and other components no longer meter the quantity on the pump.

The 2/2-way valve 39 could also be used instead of the check valve 36 directly be upstream of the fuel pump 6. The drain line 33 would then lead back into the fuel tank, for example. In this version, the delivery rate should then be measured the loss of leakage oil along with the desired injection quantity are also funded. Alternatively, the leak oil could also be used via its own, which is also effective as a differential pressure valve Intake valve directly into one or more pump cylinders 40 be returned.

As a result, the fuel flows from the fuel pump 6 virtually continuously into the high pressure part 9 and from there into the pressure chamber 13 or in the control part of the injection element 2. The latter is conventional Art trained and therefore not described in detail. A solenoid valve 60 has one that can be actuated by the control unit 31 Magnet core 22 and a magnet armature 62 with a valve body 38 and is attached to the upper end of a housing 25. The one from the high pressure part 9 coming line 9 'branches on the one hand into the pressure chamber 13 in front of the injection opening 4 and the other into an annular chamber 47, which inside of a valve body arranged in this housing 25 is limited. A movable valve body 26 and closes on the latter a the injection opening 4 closing nozzle needle 15, which in Closing state is shown. When the solenoid valve 60 is opened by the fuel flowing away through the opening 57 Pressure reduction above the nozzle needle 15, as a result of which it remaining pressure in the chamber 13 is raised and thereby Fuel through the injection opening 4 into the combustion cylinder can flow. The interaction of the nozzle needle 15 with the Valve body 26 causes an optimal opening or closing speed the nozzle needle. For this purpose there are still compression springs 96, 97 between these and the nozzle needle 15 and the housing 25 arranged, which has a spring force in the closing direction of the nozzle needle cause. Furthermore, 25 lines 10 are in the housing for Leakage oil contained in the injection element 2.

The current regulator 8 is illustrated in detail in FIG. He instructs controllable throttle valve 252 and a series-connected one Pressure correction throttle valve 253, wherein the throttle valve 252 advantageously from a needle valve with a long-stroke solenoid and is formed with or without position feedback from the same. For Achieving a constant pressure differential across valve 252 is that Pressure correction throttle valve 253 before or, as shown, after the former provided, which its flow cross-section depending on the pressure drop changes over the throttle valve 252. The throttle valve 252 delivers the desired injection quantity and, if necessary, an additional one Flow rate to compensate for leakage losses by controlling its Flow cross-section. Instead of a throttle valve could also a clocked closing valve can be used, which preferably at given clock frequency by appropriate pulse width modulation would deliver the desired injection quantity.

In all the exemplary embodiments according to the above description the pressure in the high-pressure part connected to the injection element 2 9 measured by the control unit 31 and compared there with a target pressure and if a deviation is found, the injection quantity or the power corrected the fuel pump and / or an emergency operation program switched on. With small deviations in the injection pressure for example, the injection quantity at the injection elements adjusted by correcting the spraying time. If individual injection elements are recognized as responsible for these deviations the correction only on this. With larger deviations, too corrected the pump delivery rate, or an injection element completely switched off and the pump delivery to the lower active number of cylinders adjusted. In the worst case, there is still one minimal emergency program to use, which with reduced performance Should allow travel to a service station.

Claims (10)

1. Fuel injection arrangement (30) for an internal combustion engine, in particular for a diesel engine (1), with, for each combustion cylinder (110), at least one injection member (2) controlled by a control device (31), which injection member comprises an injection opening (4) leading into the cylinder (110) and able to be closed by the latter and a pressure chamber (13) located in front of the latter, which pressure chamber (13) is connected to a high pressure part (9) supplied by a fuel pump (6), which comprises a pump piston (41) guided in a cylinder (40), depending on the engine speed, load and load variation, as well as a quantity-dosing device (120) in the fuel supply to the fuel pump (6), which delivers the injected quantity of fuel required in the combustion cylinders (110) and ascertained by the control device (31), characterised in that the quantity-dosing device (120) comprises a throttle or closing valve (39) able to be actuated by the control device (31), a chamber (35) connecting thereto and a non-return valve (36) located between this chamber (35) and the cylinder (40) of the fuel pump (6), and that provided furthermore for the leakage quantity of fuel originating from the injection member (2) is at least one leakage connection line (33), which leads from the injection member (2) into the chamber (35).
2. Fuel injection arrangement according to Claim 1, characterised in that the fuel pump (6) is constructed as a radial piston pump and the throttle or closing valve (39) is constructed as a 2/2-way valve.
3. Fuel injection arrangement according to Claim 1 or 2, characterised in that a line (12') is provided starting from the preliminary feed pump (243), connected in parallel to the fuel pump (6) and leading into the high pressure part (9) and provided with a non-return valve (42), with which line (12') a build up of pressure in the high pressure part (9) is facilitated by the preliminary feed pump (243).
4. Fuel injection arrangement according to Claim 3, characterised in that the preliminary feed pump (243) is operated electrically.
5. Fuel injection arrangement according to one of Claims 1 to 4, characterised in that the leakage-collection line (33) leads by way of a non-return valve (37) or a differential pressure valve into the chamber (35).
6. Fuel injection arrangement according to one of Claims 1 to 5, characterised in that the pressure reservoir (9") and the high pressure lines (9') of the high pressure part (9) are surrounded by a hose-like casing (91) forming an annular gap (91'), which casing opens into the fuel tank (34) or the like.
7. Fuel injection arrangement according to one of Claims 1 to 6, characterised in that associated with the injection members (2a) is a fuel pump (6a) with a quantity-dosing device (120) for the fuel and an additional high pressure pump (6b) separated therefrom, with or without a quantity-dosing device (120) for a separate medium for the control of the injection members (2a).
8. Fuel injection arrangement according to Claim 7, characterised in that the pressure produced by the additional high pressure pump (6b) on the separate medium is higher than the pressure produced by the fuel pump (6a) on the fuel.
9. Method for monitoring a fuel injection arrangement according to one of Claims 1 to 8, characterised in that the pressure in the high pressure part (9) connected to the injection member (2) is measured and compared with a reference pressure and if a deviation is ascertained, the opening duration of the injection member (2), then the delivery quantity of the quantity-dosing device (120) is varied respectively adjusted to provide a correction.
10. Method according to Claim 9, characterised in that on ascertaining a deviation of the pressure in the high pressure part (9), which has occurred outside a tolerance limit which can be selected, respectively adjusted, or a recognisable defective behaviour of an injection member (2) due to a nozzle cup fracture or cable fracture, the injection member is switched off, the delivery quantity of the quantity-dosing device (120) is correspondingly adapted and a warning or location of the defect is indicated.

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