EP1920156B1 - Fuel injection system for an internal combustion engine - Google Patents

Abstract

A fuel injection system according to the invention has a valve which is mounted at the inlet side upstream of an injector, the valve body of which valve can be adjusted by means of an adjustment device whose adjustment force is limited to a value which is lower than the force required to adjust the valve body in the opening direction when said valve body, in the closed position of the valve, is subjected to differential-pressure-dependent loading as a result of a fault.

Description

The invention relates to a fuel injection system for an internal combustion engine according to the preamble of claim 1.

A fuel injection system of the aforementioned type is known from DE 195 48 610 A1 known. It is in this system, the volume of the downstream injection injector supplied limiting and additional as a quantity limiting valve also differential pressure dependent and working as a check valve, external energy controlled 2/2-way valve provided. The actuating device associated with the valve operates magnetically, and the valve body can be loaded in the direction of its open position via a restoring force formed by a variable electromagnetic field. This is intended to enable a mode of operation of the valve in which this is controlled as a function of operating parameters of the internal combustion engine, in particular as a function of the respectively permissible maximum injection volume of the downstream fuel injector. Such a design requires a high control effort and requires differential pressure dependent high actuating forces.

The invention has the object of providing an injection system of the type mentioned in such a way that both the control effort and the energy requirements of the actuator are reduced, and this configuration due to a total of reduced energy consumption.

In the solution according to the invention, in which the injection injector and the upstream valve are energized and opened in the same time range, the energy requirement of the valve is essentially limited in the upper limit to the value required to overcome the differential force plus a safety threshold established in the respective phase between successive injections in undisturbed operation. If the injection injector operates without leakage or at least without leakage, only slight differences in pressure result, and the actuating force in the opening direction resulting from the pressure differences, that is to say from the differential pressure, is only slight. Greater pressure differences are an indicator of impermissible leakage or other disturbances in the transition from the valve to the subsequent injector, and such pressure differences corresponding forces should not be overcome consciously in the inventive solution, so that appropriate restoring forces are not applied.

In addition, in the solution according to the invention, the overflow of the valve body of the injection injector inlet side upstream valve is substantially throttle-free, so that resulting from such throttling restoring forces are also not overcome in the supply of the fuel injector also corresponding throttle losses can be avoided, which the Total energy consumption lowers.

Since the actuating force of the actuating device must also be only a relatively small safety threshold above the closing force, which corresponds to the pressure difference effective at the valve body during trouble-free operation of the injection injector and the injection injector, no high security marches are required for the design of the actuating device. so that also structurally simple and easy adjusting devices are usable, so in particular magnetic actuators.

The application of the teaching of the invention is not limited to in the direction of the valve body of the injection injector upstream valve überströmbare valves, but also to realize in connection with valves, the valve body is overflowed transversely to the direction of adjustment and thus loaded differential pressure in his leadership, which is made This differential pressure-dependent load of the respective adjustment results in counteracting frictional forces, so that these friction forces must be taken into account for the design of the adjusting device.

In the context of the invention, the valve upstream of the injection injector according to the invention can also be used in conjunction with injection injectors which, by design, operate with larger leaks. In conjunction with such solutions in which the valve also works with largely unthrottled overflow, it proves useful to provide a memory unit in the bypass to the valve, which balances the respective leakage volume biased to operating pressure within the allowable leaks.

For such a storage unit according to the invention is a structure in which in a housing-side receiving space, a valve piston is provided displaceably adjustable and pressure-dependent adjustable against spring force, so that the piston can be moved to compensate for the leakage volume. Chuer unit with a slidably guided in the receiving space, the storage volume delimiting valve piston the tightly guided valve piston can also be used to shut off the storage volume against the drain connection to the injector, so that with uncontrolled flow of fuel through the injector in case of malfunction of the injector via the storage unit also a shut-off function can be performed.

In the context of the invention, it may further be expedient to arrange upstream of the injection injector upstream valve again a Mengenbegrenzungsventil, which is designed as throttled overflowed Mengenbegrenzungsventil and the function of the uncontrolled inflow of fuel to the combustion chamber of each cylinder to be supplied by Failure of the injector, for example, tearing off the nozzle cap and / or in case of failure of the valve, in particular snagging of the valve in its open position to prevent another inflow of fuel to the internal combustion engine.

Fig. 1

eine schematische Darstellung einer Brennkraftma- schine mit ihrem Kraftstoff-Einspritzsystem,

Fig. 2

in schematisierter Schnittdarstellung das in der Leitungsverbindung einer Hochdruckquelle zu einem Einspritzinjektor des Kraftstoff-Einspritzsystemes liegende erfindungsgemäße Ventil in einer bevorzug- ten, erfindungsgemäßen Ausgestaltungsform mit Über- strömung in Stellrichtung,

Fig. 3

eine weitere Schemadarstellung, bei der dem Ventil als Bestandteil einer Ventilanordnung anströmseitig ein überströmbares Mengenbegrenzungsventil vorgela- gert ist,

Fig. 4

in einer der Fig. 3 entsprechenden Darstellung eine Ventilanordnung, bei der das Ventil im Bypass zu einem nicht überströmbaren Mengenbegrenzungsventil liegt, zu dem anströmseitig vorgelagert ein ü- berströmbares Mengenbegrenzungsventil vorgesehen ist, und

Fig. 5

eine weitere Bauform eines im Rahmen der Erfindung nutzbaren Ventiles im Schema, wobei das Ventil quer zur Stellrichtung überströmt wird.

Further details and features of the invention will become apparent from the claims. Furthermore, the invention will be explained below with reference to an embodiment. Show it:

Fig. 1

a schematic representation of an internal combustion engine with its fuel injection system,

Fig. 2

FIG. 1 is a schematic sectional view of the valve according to the invention lying in the line connection of a high-pressure source to an injection injector of the fuel injection system in a preferred embodiment according to the invention with an overflow in the direction of adjustment, FIG.

Fig. 3

a further schematic representation, in which the valve as an integral part of a valve arrangement on the upstream side an overflowable quantity limiting valve is vorgela- siege,

Fig. 4

in one of the Fig. 3 corresponding representation of a valve arrangement in which the valve is in bypass to a non-flowable quantity limiting valve, upstream of which upstream ü üströmströmbares quantity limiting valve is provided, and

Fig. 5

a further design of a valve usable in the context of the invention in the scheme, wherein the valve is overflowed transversely to the direction of adjustment.

In Fig. 1 For example, a fuel injection system 2 is shown for an internal combustion engine 1 operating as a diesel engine. The injection takes place, as shown in the figure for a cylinder of the multi-cylinder internal combustion engine 1, each to a combustion chamber 3 via an injection nozzle 12 of an injection injector 7, which is connected to a fuel supply line 11, starting from a fuel tank 10, a low-pressure fuel pump , and arranged downstream as a high-pressure source, a high-pressure fuel pump 5 with downstream high-pressure accumulator 6 are arranged. From the high-pressure accumulator 6 from branching the supply of the individual cylinders associated injection injectors 7, wherein each of the injectors 7 is preceded by a respective valve assembly 8. The control of the injectors 7 takes place, as indicated schematically, via a control and regulation unit 4.

In the Fig. 1 only schematically indicated valve assembly 8, as in 3 and 4 illustrated, formed by a foreign energy driven according to the invention valve 14, or comprises such a valve 14. A valve 14 is in Fig. 2 shown in a preferred embodiment of the invention, the direction of flow is illustrated by the arrow 31.

The valve 14 has as an adjustable locking member on a valve body 23 and includes between inlet side and outlet portions 15 and 16 of the fuel supply line 11 and connected to these end pieces 27, 28, which are connected via an axial clamping connection 29 sealingly, wherein the clamping connection 29 through as housing-like clamping sleeves 36, 37 designed housing halves is realized, the radial shoulders of the end pieces 27, 28 overlap.

In the embodiment according to Fig. 2 the drain-side, the section 16 associated end piece 28 is formed as a receptacle for the valve body 23 and has a corresponding bore 30 which is widened in diameter relative to the cross section of the portion 16 of the fuel supply line 11. The guided in the bore 30 valve body 23 runs with a poppet 33 on a seat surface 32 in the transition of the bore 30 on the section 16. The valve cone 33 is in turn connected to a shaft part of the valve body 23, which forms the armature 34 of a magnetic actuator 26 formed as a hollow shaft. The magnetic actuator 26 comprises a magnetic coil 35 which is arranged to surround the end piece 28 in a radial recess of the clamping sleeve 37 and in axial extension of a threaded neck of the clamping sleeve 36, which is overlapped by a discontinuing provided for clamping sleeve 37 collar and screwed against it.

The valve cone 33 and the end piece 28 in its in the bore 30, the armature 34 as a shaft portion receiving portion 45 which lies in the Umschließungsbereich of the magnetic coil 35, consist of non-magnetic material, as illustrated by dashed lines.

In the region of the magnet armature 34 embodied as a hollow shaft, the valve body 23 flows centrally, in the area of the valve cone 33 overflowed circumferentially, and the respective free flow cross sections correspond in the open position of the valve body 23 substantially the flow cross sections in the sections 15, 16, so that in the Open position of the valve body 23 is given an at least largely unthrottled flow or overflow, which at most a small actuating force in the direction of the closed position of the valve body 23, the in Fig. 2 shown has resulted. Such a force in the closing direction, instead of and / or in addition, are also applied via a support spring 46, as it is preferably arranged in extension of the armature 34 forming hollow shaft in support against the tail 27. The at least largely unthrottled flow or overflow is expedient, since the valve 14 is open during the injection phase and a reduction of the injection pressure would be associated with the throttling. Therefore, it is particularly the application of spring force to the valve body 23.

The magnetic actuator 26 is energized as part of the generally designated 25 actuating device via the line connection 38, in the time range of injection of the injection injector 7, in the fuel supply line 11, the valve assembly 8, ie in particular the valve 14 according to the invention, which, as in Fig. 1 dashed lines indicated, thereby easily achieve that over the control unit 4 an approximately simultaneous energization of the injector 7 and the magnetic actuator 26 takes place. Thus, the supply of fuel to the injector 7 is released via the valve 14 in the time range of the injection, and with completion of the respective injection is blocked via the valve cone 33 and the fuel flow in the direction of the injection injector 7.

If the injection injector 7 operates without leakage or virtually free of leakage, the injection injector 7 thus shows trouble-free operating behavior in accordance with its respective design, then there is substantially no pressure drop in the operating phase lying between successive injections in the outflow-side section 16 of the fuel supply line 11. Thus, there is no pressure difference between the inlet-side line section 15 and the outlet-side line section 16, which would prevent opening of the valve 14 by adjusting the valve body 23 via the magnetic actuator 26 whose actuating force is designed for undisturbed operation. If there is a pressure drop in the section 16 of the line connection 11 due to leaks at the injection injector 7 or in the inlet to the injection injector 7 in the phase between successive injections, this results in an increased differential pressure and thus a higher loading of the valve body 23 in the direction of its closed position Force. If this closing force, also in consideration of the force of the support spring 46, greater than the acting on the solenoid actuator 26, acting in the opening direction of the valve 14 actuating force, the valve 14 via the magnet plate 26 can not be opened and it we over the valve 14 supplied injector cut off from the fuel supply, so that leakage-induced damage to the internal combustion engine through uncontrolled fuel flow on the cylinder, and thus caused by, uncontrolled combustion processes can be avoided.

Unwanted, caused by fault combustion processes may also be due to the fact that the valve 14 has a malfunction, for example, in an open position, such as stuck by jamming, or in that the injection nozzle 12 breaks off the nozzle cap, so that the throttling effect of No spray holes. Such errors would lead to an influx of fuel to the combustion chamber in excess. In order to protect an injection system of the above-described type against this, shows Fig. 3 This comprises a housing 51 and a receiving space 52 which lies in the flow path of the fuel supply line 11, wherein of the housing-side pipe parts of the inlet-side pipe part 54 and the outlet-side pipe part are designated by 55. Between these line parts is located within the receiving space 52 of the valve piston 53, which is supported against the inlet direction (arrow 31) via a spring 56 and the counter to the spring force from its inlet-side stop position is adjustable in a drain-side stop position. The related stroke is designated H.

In the in Fig. 3 shown, inlet-side stop position is defined by the valve piston 53 a stroke H corresponding stroke volume, which is at least equal to, but preferably greater than the maximum injection volume of the injection injector. 7

Open valve 14 provided that the valve piston 53 is adjusted due to the given inflow side pressure against the force of the spring 56 by a stroke, to the a stroke volume correlates, which corresponds to the injection volume. If a discharge volume exceeding the tolerance value exceeds the maximum permissible injection volume, then the valve piston 53 moves into its blocking position.

At within the predetermined operating limits injection volumes of the valve piston 53 moves only over a portion of its maximum stroke H, and it is the extent displaced stroke volume in the injection pauses of the downstream injection injector 7, so balanced when the fuel supply to the combustion chamber 3, characterized in that the valve piston 53 "leaking" in the receptacle 52 is guided. Such a leaking guide can be achieved by appropriate game design between the valve piston 53 and receptacle 52, or by otherwise provided throttled overflow. In the illustrated embodiment according to Fig. 3 the valve piston 53 is sealingly guided via annular collars 57 in the receptacle 52 and there are associated with these annular collars 57 throttling overflow 58.

By connecting in series such a flow control valve, in which the overflow 58 form a Rückschiebebypass with a valve 14 - the valve 14 and the flow restrictor 15 form a valve assembly 8 - a solution is shown, which for Injektinjektoren 7, in which in the phases of non-injection no or a relatively small leakage is given, with a simple structure a sensitive appealing protection is achieved. By the overflow 58, so the Rückschiebebypass namely a tightly tolerable, "leaky" leadership of the valve element, and excessive leaks or the like cause that in addition to the injection volume each leaking a leak volume, so that if only the injection volume is replenished, ultimately the valve piston 53 goes on strike. The same is the case if, for other reasons via the connection between the flow control valve 50 and the injection injector 7 an impermissibly high amount of fuel flows.

While in the basic arrangement according to Fig. 3 Leaks as well as other inadmissibly high outflow losses can be detected via a valve assembly 14 and quantity limiting valve 50 existing valve assembly 8 for injection injectors, and at the same time the fuel supply to the injection injector can be prevented via the valve assembly 8, when the fuel injector 7 is configured in a form in the case of failure-free operating behavior assuming only small outflow losses or leakages occur during non-injection, the exemplary embodiment according to FIG Fig. 4 on injectors 7, which are designed so that arise in non-injection relatively larger leaks. For this purpose, in addition to the exemplary embodiment in the exemplary embodiment Fig. 3 provided in parallel, ie in the bypass to the valve 14, a biased storage or buffer volume embodied in a storage unit 60, which is structurally similar to a flow control valve 50, but deviating therefrom in the receiving space 62 of the housing 61 tightly guided valve piston 63 has. This also lies axially between an inlet 64 and a drain 65, wherein the inlet side is connected to the inlet-side connection 15 and the outlet side to the outlet-side connection 16 of the valve 14. The valve piston 63 is again loaded by a spring 66 on its inlet-side stop position, and to move against the force of the spring 66 in response to the pressure difference between the inlet side and drain side in its drain-side stop position. The shut off via the valve piston 63 stroke volume is only with the outlet side port 16th the valve, or lying between the valve 14 and the injection injector 7 portion of the fuel supply line 11 in connection.

Closes the valve 14, so enter through the injector-side leakage outflow losses that would lead to a downstream pressure drop, if they were not compensated by the stored in the storage element 60 and pressurized fuel volume. If these outflow losses resulting in the respective phases of the non-injection are greater than permissible, they can no longer be compensated for via the volume of the storage unit 60. Accordingly, there are differences in pressure between the inlet side and the outlet side of the valve 14, by which this is kept closed. If the losses remain within the permissible limits, the storage volume in the injection phases is replenished in each case.

In addition is in Fig. 4 , analogous to Fig. 3 upstream upstream of the valve 14, a flow control valve 50 is provided which in construction and function that according to Fig. 3 equivalent. Reference is made to the relevant comments above.

It is made possible by the separate arrangement of a limited in their storage volume, system pressure dependent biased and structurally designed in the manner of a flow restrictor memory unit 60 in parallel to the valve 14 and the upstream arrangement of a flow control valve 50 to the valve 14 a separate and thus in the respective sensitivity matched detection of leaks and / or other drainage losses, wherein the inlet side port 64 of the storage unit 60 is not via the flow control valve 50, although this is a preferred design.

To illustrate that the inventive solution not to a valve 14 of the in Fig. 2 shown type is bound with overflow in the direction of adjustment, although this is a preferred solution within the scope of the invention and if an embodiment according to Fig. 2 is also expedient in terms of a particularly sensitive response is in Fig. 5 a solution for a valve 14 in the form of a slide valve 70 shown, which is overflowed transversely to the direction of adjustment. The overflowable transversely to the direction of adjustment slide is denoted by 71, the overflow direction in turn illustrated by the arrow 31. In the illustration, the slide 71 assumes its blocking position, the adjusting device 72 is in turn illustrated as a magnetic adjusting device. The slider 71 is provided with an overflow opening 73, which is indicated by dashed lines.

The situation shown corresponds to a closed position, and at a pressure difference between inflow side and outflow side of the slide 71 is subjected to force transversely to its direction of adjustment, resulting in the slide 71 to be intercepted shear forces corresponding frictional forces against the slide housing 74. The related by such pressure differences supporting forces between the slider 71 and the housing 74 are illustrated as transverse forces to the direction of adjustment of the slider by arrows 75.

Since from mentioned pressure differences, eg excessive leakage, when the injector gets stuck in its spray position, etc. according to the size of the pressure differences considerable supporting forces, and thus an adjustment of the slide 71 counteracting frictional forces can result Also, according to these frictional forces, considerable restoring forces may be necessary.

A corresponding power supply can, as already described, be limited according to the invention, so that at correspondingly high pressure differences of the corresponding, required to adjust the slide 71 actuating force requirement can not be met, with the result that at pressure differences exceeding the corresponding limits, the slider 71st remains in its blocking position and thus can not be adjusted in its open position despite appropriate action on the adjusting device 72, wherein with respect to the power requirement to take into account that possibly also the force of acting in the direction of the closed position spring 46 is overcome.

Since the energization of the adjusting device 72 for adjustment in the time range of the energization of the injector - open the injector for injecting and opening the valve 14 in the same time range - takes place, without further control effort and a use of the adjusting device 72, which in the same way for the embodiment according to Fig. 2 applies to the adjustment of the valve in the direction of its closed position possible, instead and / or in addition to the spring 46th

Claims (17)

1. Fuel injection system for internal combustion engines (1), having a fuel high-pressure source (5), having an injector (7) which injects into a combustion chamber (3) of a cylinder of the internal combustion engine (1), and having a valve (14) which is situated in the fuel line (11) from the high-pressure source (5) to the injector (7) and which, during the time period of the injection by the injector (7), is switched into an open position by means of an actuating device (25) and whose valve body (23), in the event of a pressure drop occurring at the outlet side of the valve (14) on account of a fault, assumes a closed position and in said closed position is loaded by a force corresponding to the pressure difference existing between the inlet and outlet sides of the valve (14),
   characterized

   • in that, when the valve (14) is in the open position, flow can pass at least substantially unthrottled over the valve body (23),

   • in that the actuating force of the actuating device (25) for adjusting the valve body (23) in the opening direction from its closed position is restricted to a limit value, and

   • in that, when the injector (7) is operating without faults and is shut off together with the valve (14), the limit value corresponds to the pressure difference acting on the valve body (23) and built up between successive injections plus a safety threshold value.
2. Fuel injection system according to Claim 1,
   characterized
   in that the valve body (23) is spring-loaded in the direction of the closed position.
3. Fuel injection system according to Claim 1,
   characterized
   in that the valve body (23) of the valve (14), when in its open position, is loaded in the direction of its closed position by a flow-induced force.
4. Fuel injection system according to Claim 1,
   characterized
   in that the valve body (23) situated in an open position can be adjusted in the direction of its closed position by means of an actuating force of the actuating device (25).
5. Fuel injection system according to Claim 1,
   characterized
   in that the actuating device (25) for the valve (14) is designed as an electrically operated actuating device.
6. Fuel injection system according to Claim 5,
   characterized
   in that the actuating device (25) for the valve (14) is designed as a magnetic actuating device.
7. Fuel injection system according to Claim 6,
   characterized
   in that the valve body (23), guided in a housing bore (30), has a longitudinal region which is designed as a magnet armature (34) and which lies in the region of overlap with a surrounding magnet coil (35) on the housing, and in that the housing is composed of amagnetic material in the region (45) between the magnet coil (35) and magnet armature (34).
8. Fuel injection system according to Claim 7,
   characterized
   in that the housing bore (30) ends in the throughflow direction at a seat surface (32), and in that the magnet armature (34) bears a valve cone (33) which is assigned to the seat surface (32) and which is composed of amagnetic material.
9. Fuel injection system according to Claim 7,
   characterized
   in that the magnet armature (34) is formed as a hollow shank.
10. Fuel injection system according to Claim 8 or 9,
    characterized
    in that flow passes centrally through the magnet armature (34) and flow passes over the valve cone (33) at the outside.
11. Fuel injection system according to Claim 1,
    characterized
    in that the fuel injector (7) and the actuating device (25) of the valve (14) situated in the fuel line (11) to said injector (7) are electrically energized, and switched into the open state in fault-free operation, in the same time period, in particular approximately simultaneously.
12. Fuel injection system according to Claim 1,
    characterized
    in that, in the case of a fuel injector (7) structurally designed for at least approximately leakage-free operation, a flow rate limiting valve (50) via which flow can pass in a throttled manner is connected upstream of the valve (14) connected upstream of said fuel injector.
13. Fuel injection system according to Claim 1,
    characterized
    in that, in the case of a fuel injector (7) structurally designed for operation with leakage, an accumulator unit (60) is provided in the bypass past the valve (14) connected upstream of said injector (7), the storage volume of which accumulator unit is open towards the outlet side of the valve (14) and is pressurized via the connection of the accumulator unit (60) to the inlet side of the valve (14).
14. Fuel injection system according to Claim 13,
    characterized
    in that the accumulator unit (60) has a receiving chamber for a valve piston (63) which is guided in a sealed fashion and which movably delimits the accumulator volume with respect to the inlet side.
15. Fuel injection system according to Claim 14,
    characterized
    in that the valve piston (63) is spring-loaded in the direction of the inlet-side connection (64) and is movable under pressure loading in the direction of an opposite, blocking stop position.
16. Fuel injection system according to Claim 14 or 15,
    characterized
    in that the accumulator volume (60) corresponds to a safety margin of the maximum injection volume of the injector (7).
17. Fuel injection system according to Claim 13,
    characterized
    in that a flow rate limiting valve (50) via which flow can pass in a throttled manner is provided at the inlet side of the valve (14), upstream of the latter and the bypass branch to the accumulator device (60).

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