EP1088985B1 - High pressure fuel injector for an internal combustion engine - Google Patents

Description

The present invention relates to an injector according to the preamble of claim 1.

In the case of the known injectors, the supply of the fuel into the control chamber and into the pressure chamber arranged in the region of the nozzle needle takes place in parallel. The fuel supply hole branches into a fuel supply hole, which opens into the control space and a fuel supply hole, which opens into the pressure chamber at the nozzle needle. The branching from the fuel supply bore into the control chamber and the nozzle chamber runs in the region of a throttle plate. In this case, problems often occur at the branch point of the fuel supply bore to the control chamber and the pressure chamber in the separation region of the throttle plate and injector body, namely, where due to the prevailing high pressures and the very hot fuel special seals (metal seals) are required. The still occurring leakage is returned to the tank in such injectors. Since the leak has a high temperature, additional cooling of the tank is necessary. Moreover, the power loss of the pump is very high, since the leaking leakage causes a loss of pressure in the separation area.

From EP-A-0921301 an injector for an internal combustion engine is known which comprises an injector body having an injector body portion and a nozzle body portion with an axially extending bore. A fuel supply bore opens into the axial bore in the injector body, wherein a displaceable control piston is arranged in the axial bore. Above the control piston, a control chamber is arranged, wherein a control chamber relieving controllable valve is provided. In addition, the injector includes an extending through the axial bore, A nozzle needle communicating with the spool for opening and closing an injection port, and a nozzle spring biasing the nozzle needle into a needle seat in the region of the injection port. The fuel supply bore opens into the axial bore in a region below the control piston and the supply of fuel into the control chamber takes place from a region of the axial bore below the control piston through a bore in the control piston.

It is an object of the present invention to provide an injector in which leakage can be avoided.

This object is achieved by the features of claim 1.

By supplying the fuel in the axial bore in the injector body below the control piston and the forwarding of the same from this area in the injection space in the area the injection opening and the bore in the control piston in the control chamber, eliminates the above-mentioned branching point and consequently the risk of leakage in a parting plane. The fuel passes directly into the axial bore in the injector body and further along the nozzle needle to the injection port. In this way, the efficiency of the injector increases.

Further advantageous embodiments of the invention are specified in the dependent claims.

• Figur 1 einen erfindungsgemäßen Injektor im Schnitt zeigt;
• Figur 2 eine weitere Ausführungsform eines erfindungsgemäßen Injektors im Schnitt zeigt;
• Figuren 3A, 3B vergrößerte Darstellungen zweier Positionen des Steuerkolbens im Schnitt zeigen;
• Figuren 4A, 4B zwei Ausführungsformen des Führungskörpers zeigen und
• Figur 5 eine dritte schematische Darstellung eines erfindungsgemäßen Injektors zeigt.

The invention will be further described with reference to the accompanying drawings, in which:

• Figure 1 shows an injector according to the invention in section;
• Figure 2 shows a further embodiment of an injector according to the invention in section;
• Figures 3A, 3B show enlarged views of two positions of the control piston in section;
• Figures 4A, 4B show two embodiments of the guide body and
• Figure 5 shows a third schematic representation of an injector according to the invention.

FIG. 1 shows an injector 10. The injector 10 includes an injector body 20 which is divided into an injector body portion 30 and a nozzle body portion 40. Through both sections 30,40 extends an axial bore 50. In the injector body 20, a Kraftstoffzuführbohrung 60 is formed, which is in communication with a rail (not shown). The Kraftstoffzuführbohrung 60 opens below a control piston 70 in the through the injector body 20 extending axial bore 50. The control piston 70 is fixedly connected to a nozzle needle 80, which extends through the axial bore 50 in the injector 20 body. The fuel thus passes through the Kraftstoffzuführbohrung 60 in the axial bore 50 in the injector body 20. Consequently, the entire axial bore 50 is filled below the control piston 70 in the injector body 20 with fuel, which passes within the axial bore 50 into the region of an injection port 290.

The control piston 70, the injector body 20 and a not shown in detail electrically controllable valve 90 define a control chamber 100. In the control piston 70, a bore 110 is formed, from which an inlet throttle 120 and an inlet throttle 130 open into the control chamber 100. The inlet throttle 120 extends obliquely in the control piston 70 and the inlet throttle 130 extends from the bore 110 axially through the control piston 70. On the control chamber 100 facing the end face of the cylindrical control piston 70, an extension 140 is formed. The extension 140, in the center of which the inlet throttle 120 is located, is the stop for the control piston 70 and thus for the nozzle needle 80. The inlet throttle 130 opens in the region of this extension 140 into the control chamber 100, whereas the inlet throttle 120 in a region of the end face of the control piston 70 opens into the control chamber 100, which continues in the stop position of the control piston 70 in a discharge throttle 150 in the valve 90. It should be noted at this point that it is also conceivable to provide only one or more than two outlet throttles in the control piston 70.

The nozzle needle 80 is biased at rest by a spring 160 to a needle seat 170 in the nozzle body portion 40. The spring 160 is supported via a dial 180 on a shoulder 190 in the injector body 20. The power is transmitted to the nozzle needle 80 via a formed on the nozzle needle 80 annular shoulder 200. For the operation of the injector 10, it is important that the control piston 70 and the needle seat 170 in the nozzle body portion 40 are arranged exactly concentric. This required, exact axial position of needle seat 170 and control piston 70 is ensured in the case of the divided injector body 20 shown in the embodiments of FIGS. 1, 2, 5, 6 by centering bodies 210a, 210b.

As can be seen in FIG. 1, the centering body 210a is arranged in the form of a centering ring in a recess 220 on the outer circumference of the injector body section 30 and nozzle body section 40 in the contact region of the two body sections 30, 40. However, it is also conceivable to use the centering body 210b on the inner circumference, i. in the axial bore 50 of the injector body 20 so that it is located inside (Figure 2). In both cases, the centering bodies 210a, 210b are introduced under tension.

In the embodiment of the injector 10 according to FIG. 1, a guide body 230a for the nozzle needle 80, through which the nozzle needle 80 extends, is arranged in the region of the axial bore 50 in the injector body 20 close to the needle seat 170. The centering body 230 is necessary due to the long and slender nozzle needle 80 to ensure accurate needle guidance and accurate operation of the injector 10. The centering body 230 is urged by a spring 240 in the outer region of the cylindrical Injektorkörperbohrung 50. The spring 240 is supported on the nozzle needle side via the annular shoulder 200 on the nozzle needle 80. The nozzle needle 80 is guided in a concentrically arranged bore 250 in the guide body 230a.

As can be seen in FIG. 4A, the guide body 230a can be made of an annular starting material which is deformed symmetrically such that it is in each case at four points a, b, c, d, A, B, C, D on the nozzle needle 80 or abuts against the axial bore 50. After deformation and a In the hardening process, the guide body 230a is ground concentrically on its outer circumference A, B, C, D and on the inner surfaces a, b, c, d. By providing a slight interference fit between the centering body 230a and the nozzle body portion 40, the need for the spring 240 may be eliminated.

According to a further embodiment, as shown in FIG. 4B, the centering body 230b may be made of an edged starting material. After hardening of the centering body 230b, only grinding of the outer X and inner Y diameters is necessary.

The embodiment of the injector 10 of Figure 2 differs from that of Figure 1 only by the implementation of the power transmission from the nozzle spring 160 to the nozzle needle 80. This is done via a spring ring 260 which is arranged in a groove 270 in the nozzle needle 80. About the spring ring 260, a spring plate 280 is pushed to prevent jumping out of the spring ring 260.

The guide body 230a, 230b and the spring 240 are not shown in the embodiment of Figure 2 for the sake of clarity, but can of course also be used in this embodiment.

5 shows a further embodiment of the injector 10 is shown in a schematic representation. In contrast to the embodiments according to FIGS. 1 and 2, the injector body section 30 and the nozzle body section 40 are formed in one piece. This eliminates the need for a centering between the two sections 30 and 40. It should not be ruled out, however, the embodiment of Figure 5 according to the embodiments of Figures 1 and 2 as in the injector body portion 30 and nozzle body portion 40 separate injector 20 perform.

The nozzle spring 160 biasing the nozzle needle 80 into the needle seat 170 is arranged in the embodiment of FIG. 5 in the control chamber 100. However, this has, as described in the embodiments described above, also via the bore 110 in the control piston 70 connection with the area below the control piston 70, in which the fuel supply takes place. The nozzle spring 160 has a rectangular cross section. As a result, the harmful volume of the control chamber 100 is reduced. In addition, a filler in the control room 100 is arranged.

The injector 10 described in FIGS. 1 to 4 operates as follows:

In the starting position according to FIG. 3A, the control piston 70 is in a lower position. The nozzle needle 80 is displaced downwards into the nozzle needle seat 170 and closes the injection opening 290. The outlet throttle 150 and a hole 300 that adjoins it are closed by the electrically controllable valve 90. Via the two inlet throttles 120, 130, the control chamber 100 has access to the space below the control piston 70, which is under system pressure due to the connection of the fuel supply bore 60 to the rail.

To initiate an injection, the control chamber 100 is relieved by activating the valve 90 and simultaneously opening the outlet throttle 150, ie fuel in the control chamber 100 flows via the outlet throttle 150 in the valve 90. The control piston 70 shifts due to the now prevailing pressure difference - pressure in the control chamber 100 is lower than the system pressure below the control piston 70 - upwards. As soon as the control piston 70 with the extension 140 reaches the upper stop, the inlet throttle 130 is closed.

To complete the injection, the valve 90 is driven again, so that the outlet throttle 150 is closed. First, the fuel flows through the inlet throttle 120. As soon as the control piston 70 moves slightly downward, the fuel can also pass through the inlet throttle 130 in the control chamber 100 and the control piston moves faster down and urges the associated nozzle needle 80 in their Needle seat 170, which closes the injection port 290. The inlet throttle 120 has a smallest possible flow cross-section, the inlet throttle 130 has a large flow cross-section in the interest of fast needle closing.

An advantage of this embodiment of the injector according to the invention is that the nozzle needle 80 and the control piston 70 form a common production-favorable component. The injector 10 is leak-free and consists of only a few parts. The design of inlet and outlet throttles is a compromise in common rail systems. The throttle combination described allows the throttle cross-sections to be designed optimally. As a particular advantage, the control leakage can be avoided during the injection to a small residual value, in the illustrated form as a leak-like injector all leakage losses are almost eliminated.

Claims (8)

1. An injector (10) for an internal combustion engine having direct injection, comprising:

   - an injector body (20) which has an injector body section (30) and a jet body section (40) and includes a hole (50) which extends axially,

   - a fuel supply hole (60) in the injector body (20), said fuel supply hole opening into the axial hole (50),

   - a control piston (70) which can move in the axial hole (50),

   - a control chamber (100) which is arranged above the control piston (70),

   - a triggerable valve (90) which can reduce the pressure in the control chamber (100),

   - a jet needle (80) for opening and closing an injection opening (290), said jet needle extending through the axial hole (50) and connecting to the control piston (70), and

   - a jet spring (160) which pretensions the jet needle (80) in a needle seat (170) in the area of the injection opening,

   - wherein the fuel supply hole (60) opens into the axial hole (50) in an area below the control piston (70),

   - wherein the supply of fuel into the control chamber (100) takes place via a hole (110) in the control piston (70) from that area of the axial hole (50) which is below the control piston (70),
   wherein the control piston (70) is designed as a cylinder having a coaxially arranged extension (140) on that face which is oriented towards the control chamber (100),
   wherein two supply throttles (120, 130) in the form of throttle holes lead from the hole (110) into the control chamber (100), wherein one (130) of the two supply throttles (120, 130) opens into the control chamber (100) centrally in the area of the face of the extension (140), characterised in that the extension (140) closes the one supply throttle (130) when an upper stop is reached.
2. The injector as claimed in Claim 1, characterised in that the injector body section (30) and the jet body section (40) are designed as two parts.
3. The injector as claimed in one of the Claims 1 or 2, characterised in that a centring body (210a, 210b) is provided in the contact area of the injector body section (30) and the jet body section (40), in order to allow the exact concentric arrangement of the control piston (70) in relation to the needle seat (170).
4. The injector as claimed in one of the Claims 1 to 3, characterised in that the load transfer from the jet spring (160) onto the jet needle (80) takes place via transfer means (200; 260, 270, 280) which are arranged on the jet spring (160).
5. The injector as claimed in one of the Claims 1 to 4, characterised in that the jet spring (160) is arranged in the control chamber (100).
6. The injector as claimed in one of the Claims 1 to 5, characterised in that a guide body (230a, 230b) for the jet needle (80) is arranged in the axial hole (50).
7. The injector as claimed in Claim 6, characterised in that the guide body (230a) is produced by shaping a tubular starting material in its axial direction, such that it fits closely against the jet needle (80) and the axial hole (50) along at least three lines of contact in each case.
8. The injector as claimed in Claim 6, characterised in that the guide body (230b) is produced from a bar-shaped starting material which has a polygonal cross-section and in which a central hole is formed for holding the jet needle (80).

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