EP2852754B1 - Injector of a fuel injection system - Google Patents

Description

The invention relates to an injector of a modular common rail fuel injection system with a high-pressure accumulator integrated in the injector body, wherein the injector has an injection nozzle with axially displaceable guided, surrounded by a nozzle chamber nozzle needle, the high pressure accumulator with the nozzle chamber connecting high pressure bore, a parallel to the high pressure bore Resonator bore which communicates with the injection nozzle and opens via a resonator in the high-pressure accumulator, and has a holding body which is frontally screwed to the high-pressure accumulator forming member, in particular a storage tube and through which the high-pressure bore and the resonator bore.

Injection injectors of this type are used in modular common rail systems, which are characterized in that a part of the existing storage volume in the system is present in the injector itself. Modular common-rail systems are used in particularly large engines, in which the individual injectors may be mounted at a considerable distance from each other. The sole use of a common rail for all injectors is not useful in such engines, as it would come due to the long lines during injection to a massive slump in Ein-injection pressure, so with prolonged injection duration, the injection rate would noticeably break. In such engines, it is therefore intended to arrange a high-pressure accumulator inside each injector. Such a design is referred to as a modular structure, since each injector has its own high-pressure accumulator and thus can be used as a stand-alone module. Under a high-pressure accumulator is not a common line to understand, but it is at a high-pressure accumulator to a pressure-resistant vessel with an inlet and outlet, whose diameter is significantly increased compared to the high pressure lines, thus from the High-pressure accumulator can be discharged a certain amount of injection, without causing an immediate pressure drop.

In a common rail system, electronically controlled injection injectors are used to inject the fuel into the engine combustion chamber. The servo valves used in these injectors cause a very fast closing of the injector. When closing the injector, the fuel runs against a closed line end, wherein due to the inertia of the fuel, the pressure in front of the injector increases significantly. As a result, this pressure peak reciprocates in the high-pressure bore between the injection nozzle and the high-pressure accumulator, with strong pressure pulsations occurring at the nozzle seat, which lead to excessive wear here. The resulting pressure peaks are in unfavorable cases by up to 500 bar above the rail pressure.

One way of reducing pressure pulsations is the WO 2007/143768 A1 can be seen, wherein a parallel to the high-pressure line between the injection nozzle and high-pressure accumulator switched resonator is provided, the high-pressure accumulator side has a resonator. The resonator throttle is preferably arranged at the inlet of the resonator line into the high-pressure accumulator.

When manufacturing the resonator bore including the resonator throttle, the problem arises that, especially with injectors with a longer resonator bore, a bore offset occurs which greatly reduces the high-pressure resistance. The hole offset is achieved as follows. In the course of production, the resonator bore is first drilled in the form of a blind hole with a diameter of eg 3 mm from one side of the holding body ago. Thereafter, the resonator throttle is drilled, for example, with a diameter of 0.7 - 0.9 mm from the opposite side, this hole should open as central as possible in the resonator bore for reasons of high pressure resistance. The axis of the resonator bore should thus coincide with the axis of the resonator choke. However, the required manufacturing accuracy is not feasible in practice. On the one hand, a tapping error always occurs when applying the drilling tool. On the other hand, it usually comes with longer holes to a deviation from the desired axial bore direction, which results in that one end of the bore relative to the other End of the hole is offset by up to 2% axially. Together with the tapping error this leads to the fact that the throttle bore does not open centrally into the resonator bore, but offset by up to 0.5 mm.

The invention therefore aims to realize the described resonator function in injectors with longer high-pressure wells in a structurally simple manner, without significantly impairing the high-pressure resistance.

To achieve this object, the invention essentially provides, starting from an injector of the type mentioned above, that an end portion of the high-pressure bore facing the high-pressure accumulator and an end portion of the resonator bore facing the high-pressure accumulator and having the resonator throttle is embodied in a separate component which extends between the holding body and the storage tube is inserted and fixed by the screwing of the holding body and storage tube. By means of this measure it is achieved that the production-technically unavoidable bore offset has no influence on the transition of the resonator bore into the resonator throttle. This transition is in fact arranged in the separate component, in which the problem of the hole offset due to the smaller axial length has no noticeable effect on the high pressure resistance. This is especially true when the separate component is made shorter than the holding body, so for example. is formed with an axial length of less than 100mm, preferably less than 50 mm, more preferably less than 30mm. At most, an offset occurs at the transition between the resonator bore embodied in the holding body and the end portion of the resonator bore executed in the separate component, which is less critical with regard to the high-pressure resistance.

The separate component is in this case held only by the axial force generated during screwing of the holding body with the storage tube and clamped between these two components without the need for further fasteners as it were.

In order that the torque acting on the separate component during screwing of the holding body does not lead to a rotation of the separate component, a preferred embodiment of the invention provides that the holding body and the separate component are secured against rotation by means of an axial pin.

On the one hand to ensure a secure holding of the separate component and on the other hand to create a high-pressure-tight connection, it is preferably provided that the separate component carries a conical sealing surface which cooperates with a formed on a shoulder of the storage tube conical mating surface of the storage tube. At the end face facing the holding body, the separate component preferably has a planar sealing surface which cooperates with the planar end face of the holding body.

A preferred embodiment provides that the two end sections converge towards one another. In particular, the two end sections open into a blind hole formed in the separate component. Alternatively, however, the two end sections can also run parallel to one another.

Preferably, the separate component is designed as a plate.

It is preferably provided that the resonator throttle is arranged at the inlet of the resonator bore in the high-pressure accumulator. The resonator choke is thus formed in the separate component. In this case, the resonator throttle can be designed in different lengths. For example, the resonator choke can be made relatively short so that it extends only over a short axial section, in particular via an end section of the separate component, in particular the plate, facing the high-pressure accumulator. Alternatively, the resonator choke can extend through the separate component, in particular the plate, so that its length corresponds to the axial extension of the separate component, in particular the plate.

The inventive design is particularly advantageous for injectors to bear, in which the nozzle needle for controlling its opening and closing movement of the prevailing in a fuel-pressurized control chamber pressure in the axial direction can be acted upon, wherein the control chamber with a inlet throttle having inlet channel and an outlet channel having a flow channel is in communication and at least one of the inlet or outlet channel opening or closing control valve provided is, with which the pressure in the control chamber is controlled, that the inlet throttle and the outlet throttle are formed in a throttle plate, that the control valve is formed in a valve plate and that the high-pressure bore and the resonator bore, the valve plate and the throttle plate prevail. In this case, the injector is usually designed such that an injector and / or holding body accommodating the high-pressure accumulator, the valve plate, the throttle plate and the injection nozzle are held together by a nozzle retaining nut. The high-pressure bore and the resonator bore extend through the holding body, the valve plate and the throttle plate and thereby connect the high-pressure accumulator with the injection nozzle.

The length of the resonator bore is preferably matched to the length of the high-pressure bore so that the pressure oscillations induced by the injector mutually weaken or extinguish each other.

The length of the resonator bore between the injection nozzle and the resonator throttle as well as the length of the high-pressure bore between the injection nozzle and the inlet of the high-pressure bore into the pressure accumulator are each preferably an integer multiple of the wavelength of the pressure oscillation induced by the injection nozzle.

The length of the resonator bore between the nozzle front chamber and the resonator throttle preferably corresponds substantially to the length of the high-pressure bore between the nozzle front chamber and the inlet of the high-pressure bore into the pressure accumulator.

The invention will be explained in more detail with reference to an embodiment schematically illustrated in the drawing. In this show Fig. 1 schematically a cross section of an equipped with a high-pressure accumulator injector according to the prior art and Fig. 2 a detailed representation of the junction region of the resonator in the high-pressure accumulator.

In Fig. 1 an injector 1 is shown having an injector 2, a throttle plate 3, a valve plate 4, a holding body 5 and a high-pressure accumulator 6, wherein a screwed to the holding body 5 nozzle retaining nut 7, the injection nozzle 2, the throttle plate 3 and the valve plate 4 together. At rest the solenoid valve 13 is closed, so that high pressure fuel from the high-pressure accumulator 6 via the high-pressure bore 8, the cross-connection 9 and the inlet throttle 10 flows into the control chamber 11 of the injection nozzle 2, the outflow from the control chamber 11 via the outlet throttle 12 but blocked at the valve seat of the solenoid valve 13 is. The voltage applied in the control chamber 11 system pressure presses together with the force of the nozzle spring 14, the nozzle needle 15 in the nozzle needle seat 16, so that the injection holes 17 are closed. If the solenoid valve 13 is actuated, it releases the flow through the solenoid valve seat, and fuel flows from the control chamber 11 through the outlet throttle 12, the solenoid valve armature chamber and the low-pressure bore 18 back into the fuel tank, not shown. A equilibrium pressure defined in the control chamber 11 by the flow cross-sections of inlet throttle 10 and outlet throttle 12 is so small that the system pressure applied in the nozzle chamber 19 is able to open the nozzle needle 15, which is displaceable longitudinally in the nozzle body, so that the spray holes 17 are released and an injection takes place.

Due to the inertia of the fuel in memory 6, high-pressure bore 8 and nozzle chamber 19, there are strong pressure oscillations on the nozzle seat 16 directly after the closing of the nozzle needle 15, since the flowing fuel has to be braked in a very short time. To reduce the pressure oscillations, a resonator is used. This consists of a resonator 20, which has the same length and possibly the same diameter as the high-pressure bore 8, and a resonator 21, which is attached to the memory-side end of the resonator 20 and connects them to the high-pressure accumulator 6. When the solenoid valve 13 is closed, the pressure pulse generated at the nozzle seat 16 is propagated via the nozzle chamber 19 into the high-pressure bore 8 and the resonator bore 20. At the end of the high-pressure bore 8, a reflection of the pressure pulse at the open end takes place at the transition into the high-pressure accumulator 6. At the same time, the pressure pulse running in the resonator bore 20 is reflected at the closed end on the resonator throttle 21. The two reflected pressure pulses are phase-shifted by 180 ° due to the different reflection mode (open or closed end), so that they cancel each other out in the nozzle chamber 19 when they meet. As a result, there are no further pressure pulses on the nozzle seat 16, so that significantly less wear occurs here.

The supply of high-pressure fuel from a high-pressure pump not shown in the injector 1, via a arranged on the top of the injector 1 high-pressure port 22 (topfeed injector).

In the detail view according to Fig. 2 the training of the invention is shown, with the exception of in Fig. 2 The details shown are identical to those in Fig. 1 , so that for the same components in Fig. 1 used reference numerals have been retained. Fig. 2 shows a disposed between the storage tube 25, the high-pressure accumulator 6 and the holding body 5 plate 23, which represents the inventively provided separate component. The plate 23 has a conical sealing surface 24 which cooperates with a formed on a shoulder 26 of the storage tube 25 conical mating sealing surface. The shoulder 26 of the storage tube 25 is connected via an annular groove-like recess 27 with a thin-walled, provided with an internal thread 28 portion 29 of the storage tube 25. The plate 23 is inserted between the holding body 5 and the storage tube 25 and fixed by the screw connection of these two components. The plate 23 is secured by means of at least one pin 30 against rotation. The sealing to the holding body 5 via a flat sealing point 31, which is formed by a formed on the holding body 5 facing end face plane sealing surface of the plate 23, which cooperates with the flat end face of the holding body 5. A ring seal 36 provides an additional seal.

In the plate 23, an end portion 32 of the high-pressure bore 8 and an end portion 33 of the resonator bore 20 is now formed. The two end portions extend obliquely to the injector 34 and converge toward a high-pressure accumulator-side blind hole 35, in which both end portions 32, 33 open. In this case, the end section 33 of the resonator bore 20 opens into the high-pressure accumulator 6 via the resonator throttle 21. At the flat sealing point 31, the end section 32 merges into the high-pressure bore 8 and the end section 3 into the resonator bore.

Claims (8)

1. Injector of a modular common-rail fuel injection system having a high-pressure accumulator integrated in the injector body, wherein the injector has an injection nozzle, with a nozzle needle which is guided in axially displaceable fashion therein and which is surrounded by a nozzle chamber, a high-pressure bore, which connects the high-pressure accumulator to the nozzle chamber, a resonator bore, which is connected in parallel with respect to the high-pressure bore and which is connected to the injection nozzle and which opens via a resonator throttle into the high-pressure accumulator, and a holding body, which at a face side is screwed together with the component, in particular accumulator pipe, which forms the high-pressure accumulator and through which the high-pressure bore and the resonator bore extend, characterized in that an end section (32), facing toward the high-pressure accumulator (6), of the high-pressure bore (8) and an end section (33), which faces toward the high-pressure accumulator (6) and which has the resonator throttle (21), of the resonator bore (20) is formed in a separate component (23) which is placed between the holding body (5) and the accumulator pipe (25) and which is fixed by way of the screw connection of holding body (5) and accumulator pipe (25).
2. Injector according to Claim 1, characterized in that the separate component (23) bears a conical sealing surface (24) which interacts with a conical counterpart sealing surface of the accumulator pipe (25), said counterpart sealing surface being formed on a shoulder (26) of the accumulator pipe (25).
3. Injector according to Claim 1 or 2, characterized in that the separate component (23) has, on the face side facing toward the holding body (5), a planar sealing surface which interacts with the planar face side of the holding body (5).
4. Injector according to Claim 1, 2 or 3, characterized in that the holding body (5) and the separate component (23) are rotationally secured by way of an axial pin (30).
5. Injector according to one of Claims 1 to 4, characterized in that the two end sections (32, 33) converge on one another.
6. Injector according to one of Claims 1 to 5, characterized in that the two end sections (32, 33) open into a blind hole (35) formed in the separate component (23).
7. Injector according to one of Claims 1 to 6, characterized in that the resonator throttle (21) extends through the separate component (23).
8. Injector according to one of Claims 1 to 7, characterized in that the nozzle needle (15) can, for the control of its opening and closing movement, be acted on in an axial direction by the pressure prevailing in a control chamber (11) which can be fed with pressurized fuel, wherein the control chamber (11) is connected to an inflow duct (9), which has an inflow throttle (10), and to an outflow duct, which has an outflow throttle (12), and at least one control valve (13) is provided which opens or closes the inflow or outflow duct and by way of which the pressure in the control chamber (11) is controlled.

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