Device for injecting fuel into the combustion chamber of an internal combustion engine

Abstract

A device for injecting fuel into the combustion chamber of an internal combustion engine comprising at least one injector. The injector includes an injector body, a high-pressure accumulator integrated into the injector body, an injection nozzle, a high-pressure bore, and a feed bore. The injection nozzle defines a nozzle chamber and has a nozzle needle configured to be guided in an axially movable manner and that is surrounded by the nozzle chamber. The high-pressure bore is connected to the high-pressure accumulator and the nozzle chamber. The feed bore is configured to feed high-pressure fuel to the high-pressure accumulator. Additionally, the feed bore has a lance connection positioned laterally on the injector body, is formed as a bore separate from the high-pressure bore, and connects the lance connection directly to the high-pressure accumulator.

Claims

1. A device for injecting fuel into the combustion chamber of an internal combustion engine, comprising: at least one injector including: an injector body including an accumulator tube, a holding body, and an injection nozzle, the holding body having a first end connected to the accumulator tube, the accumulator tube defining a high-pressure accumulator chamber integrated into the injector body, and the injection nozzle defining a nozzle chamber and having a nozzle needle surrounded by the nozzle chamber and configured to be guided in an axially movable manner; a high-pressure bore defined at least partially in the holding body and connecting the high-pressure accumulator chamber and the nozzle chamber; a feed bore defined at least partially in the holding body and configured to feed high-pressure fuel to the high-pressure accumulator chamber; and a lance connection positioned laterally on the holding body of the injector body, wherein the feed bore is formed separately from the high-pressure bore, and connects the lance connection directly to a portion of the high-pressure accumulator chamber defined in the accumulator tube.

2. The device for injecting fuel into the combustion chamber of an internal combustion engine as claimed in claim 1, further comprising: a resonator bore positioned in parallel with the high-pressure bore and connected to the injection nozzle, wherein the resonator bore is configured to open into the high-pressure accumulator chamber via a resonator restrictor.

3. The device for injecting fuel into the combustion chamber of an internal combustion engine as claimed in claim 1, wherein: the nozzle needle is configured to be opened and closed by being acted upon in an axial direction by a pressure prevailing in a control space that is fed with fuel under pressure; the control space is connected to a feed channel having a feed restrictor and to a drain channel having a drain restrictor; and at least one control valve is configured to control the pressure in the control space by opening or closing the feed channel or drain channel.

4. The device for injecting fuel into the combustion chamber of an internal combustion engine as claimed in claim 1, wherein the holding body is connected to the accumulator tube by being screwed at the first end to the accumulator tube.

5. The device for injecting fuel into the combustion chamber of an internal combustion engine as claimed in claim 1, wherein the holding body is interposed axially between the high-pressure accumulator chamber and the injection nozzle.

6. The device for injecting fuel into the combustion chamber of an internal combustion engine as claimed in claim 1, wherein the feed bore and the high-pressure bore both open into the high-pressure accumulator chamber at the first end of the holding body.

7. The device for injecting fuel into the combustion chamber of an internal combustion engine as claimed in claim 1, wherein the feed bore includes a first portion extending parallel to the high-pressure bore and opening into the high-pressure accumulator chamber, and a second portion extending laterally from the first portion to the lance connection.

8. The device for injecting fuel into the combustion chamber of an internal combustion engine as claimed in claim 7, wherein the first portion and the second portion are both defined in the holding body.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) The disclosure is explained in greater detail below by means of an illustrative embodiment shown schematically in the drawings. In said drawings:

(2) FIG. 1 shows schematically a cross-section of a prior art injector fitted with a high-pressure accumulator, and

(3) FIG. 2 shows a schematic illustration of the injector design according to the disclosure

DETAILED DESCRIPTION

(4) FIG. 1 shows an injector 1, which has an injection nozzle 2, a restrictor plate 3, a valve plate 4, a holding body 5 and a high-pressure accumulator 6 formed by an accumulator tube 26, wherein a nozzle clamping nut 7 screwed to the holding body 5 holds together the injection nozzle 2, the restrictor plate 3 and the valve plate 4. In the state of rest, the solenoid valve 13 is closed, with the result that the high-pressure fuel from the high-pressure accumulator 6 flows into the control space 11 of the injection nozzle 2 via the high-pressure line 8, the cross connection 9 and the feed restrictor 10, but outflow from the control space 11 via the drain restrictor 12 is blocked at the valve seat of the solenoid valve 13. The system pressure prevailing in the control space 11, together with the force of the nozzle spring 14, presses the nozzle needle 15 into the nozzle needle seat 16, with the result that the spray holes 17 are closed. If the solenoid valve 13 is actuated, it allows flow via the solenoid valve seat, and fuel flows out of the control space 11, through the drain restrictor 12, the solenoid valve armature space and the low-pressure bore 18 back into the fuel tank (not shown). A pressure equilibrium defined by the flow cross sections of the feed restrictor 10 and the drain restrictor 12 is established in the control space 11, this being so small that the system pressure prevailing in the nozzle space 19 is able to open the nozzle needle 15 guided in a longitudinally movable manner in the nozzle body, with the result that the spray holes 17 are exposed and an injection takes place.

(5) As soon as the solenoid valve 13 is closed, the drain path of the fuel through the drain restrictor 12 is blocked. Fuel pressure is built up again in the control space 11 via the feed restrictor 10, generating an additional closing force which reduces the hydraulic force on the pressure shoulder of the nozzle needle 15 and exceeds the force of the nozzle spring 14. The nozzle needle 15 closes the path to the injection openings 17, and the injection process is ended.

(6) Owing to the inertia of the fuel in the accumulator 6, the high-pressure line 8 and the nozzle space 19, there are severe pressure oscillations that the nozzle seat 16 directly after the closure of the nozzle needle 15 since the flowing fuel has to be slowed down in a very short time. To reduce the pressure oscillations, use is made of a resonator. This consists of a resonator line 20, which has the same length and the same diameter as the high-pressure line 8, and of a resonator restrictor 21, which is fitted at the accumulator end of the resonator line 20 and connects said line to the accumulator 6. When the solenoid valve 13 is closed, the pressure pulse which arises at the nozzle seat 16 propagates via the nozzle space 19 into the high-pressure line 8 and the resonator line 20. At the end of the high-pressure line 8, the pressure pulse is reflected at the open end at the transition to the accumulator 6. At the same time, the pressure pulse traveling in the resonator line 20 is reflected at the resonator restrictor 21 at the closed end. Owing to the different type of reflection (open or closed end), there is a phase difference of 180 between the two reflected pressure pulses, with the result that they cancel each other out when they meet in the nozzle space 19. As a result, there are no further pressure pulses at the nozzle seat 16, and therefore significantly less wear occurs here.

(7) In the prior art embodiment shown in FIG. 1, the high-pressure fuel is fed to the high-pressure accumulator 6 from the side of the injector 1, namely via a side feed 24. The side feed 24 comprises a lance screwed laterally into the injector 1 or a lance connection 25 (shown only in FIG. 2). The feed bore is denoted by 22 and opens into the high-pressure bore 8 at 23. Thus, during the injection by the injector 1 the fuel does not flow only from the high-pressure accumulator 6 to the injection nozzle 2 but, owing to the pressure drop, also flows directly from the feed bore 22 to the injection nozzle 2. On completion of the injection, the high-pressure accumulator 6 is refilled by the additional fuel flowing from the lance. As a result, there is only a slight fuel exchange in the accumulator by means of this additional quantity.

(8) FIG. 2 shows a highly schematized illustration of the injector 1, wherein the functional components described in detail in FIG. 1, namely the accumulator 6, the holding body 5, the valve plate 4, the restrictor plate 3 and the injection nozzle 2 are merely outlined without a detailed illustration of their individual components, as described by means of FIG. 1. FIG. 2 shows the design according to the disclosure, in which the feed bore 22 connects the lance connection 25 directly to the high-pressure accumulator 6. This has the effect that the entire injection quantity is taken from the high-pressure accumulator 6 in each injection, with the result that there is sufficient circulation of the accumulator contents over the time in operation.