EP1157203B1 - Injector for an injection system of an internal combustion engine - Google Patents

Abstract

The invention relates to an injector for an injection system of an internal combustion engine which comprises an injector head (1), a nozzle (13) for injecting fuel, a control unit for controlling the fuel transfer from the injector head (1) to the nozzle (13) and an actuator (6) for mechanically driving the control unit for controlling the fuel injection. An injector housing (2) is moulded to the injector head (1) in such a way that said injector housing (2) and said injector head (1) form one part. The injector housing accommodates at least the control unit.

Description

The invention relates to an injector for an injection system an internal combustion engine according to the preamble of the claim 1 (see EP-A-262 539).

Conventional injectors for fuel injection in Internal combustion engines are generally modular and consist of several parts arranged coaxially one above the other, such as an injector body and a control module, the mechanical connection of two axially adjacent Parts through a connecting element like an adapter sleeve, a double clamping nut or a welding sleeve.

The attachment of the injector in the cylinder head of the internal combustion engine is usually done by a so-called Clamping claw that fits the injector axially into a corresponding Press the mounting hole in the cylinder head, the Clamping claw rests on a cylindrical collar on the outside is integrally formed on the injector.

In addition, there are key surfaces on the lateral surface of the injector molded into which the clamping claw engages, causing the injector to rotate about its longitudinal axis is prevented.

The cylindrical collar and the key surfaces are used in the known injectors either directly on the injector head or attached to a hollow cylindrical union nut, which the individual parts of the injector and on their top is connected to the injector head.

A disadvantage of the injectors described above, however the variety of parts, which makes the manufacturing and assembly the injector is relatively expensive.

The invention is therefore based on the object of an injector for an injection system of an internal combustion engine create in which the effort for manufacturing and assembly is reduced.

The task is based on one of the above Injectors according to the preamble of claim 1, by the characterizing features of claim 1 solved.

The invention includes the general technical teaching, to provide an essentially one-piece injector housing, that goes into the injector head at the top and at least the control unit picks up. The injector housing preferably takes but several modules of the injector open and clamped these axially against each other to provide a high pressure seal on the To create joints between neighboring modules.

By using a common housing for the essential Components of the injector can be advantageous on separate Lanyards such as clamping sleeves, double clamping nuts or welding sleeves to connect the individual parts as the individual parts of the injector already mechanically fixed by the common housing.

In addition, the common injector housing is advantageous reduces the number of high pressure sealing surfaces that could leak to the outside.

However, it is not necessary within the scope of the invention that the injector housing accommodates all components of the injector and connects with each other. For example, it is also possible that the nozzle body at the bottom of the injector via a conventional clamping nut with the injector housing is screwed while the other components of the injector, such as the control unit, in the injector housing are accommodated.

In a variant of the invention, a separate Transmission lever for transmitting the actuating movement of the actuator dispenses with the valve piston by the actuator acts directly on the valve piston. This advantageously eliminates a component of the injector, whereby the manufacturing and Assembly effort is further reduced. Furthermore is achieved by dispensing with a conventional transmission lever the durability of the injector increases because of such Component problematic in terms of service life is.

The contact surface between the actuator on the one hand and the Valve piston on the other hand is preferably so large that that due to the reduced surface pressure even with one Switching another liquid film between the actuator and the valve piston remains, which is a hydraulic Game compensation effects. The facing end faces actuator and / or valve piston are preferred convex shaped to tear off the liquid film the mechanical load during a switching operation avoid, however, the end faces can also completely be flat, what a simple length adjustment by measuring and grinding allowed.

It is preferred here between the actuator and the valve piston a spring arranged, which actuator and valve piston pushes apart in the axial direction and thus at rest the injector restores full play compensation. In addition, such a spring advantageously allows also compensation for thermal expansion.

According to a variant of the invention, the valve piston of the Injector not directly in the injector housing, but stored in a separate valve housing that inside the injector housing is arranged. This has the advantage that the valve seat of the valve piston to be hardened is thus is in the valve housing and not in the injector housing, so that no expensive heat treatment of the entire injector housing is required.

In another variant of the invention, a continuous Leakage line dispensed by the central bore for the control elements in addition to the leakage return line from the nozzle up to the control unit. As a result, the manufacturing effort for the injector continues reduced. The leakage is then above the control unit continued via a separate leakage line, the Connection of the leakage line with the central bore preferably through a radial connecting bore.

The injector according to the invention is preferably used in a common rail injection system used, however, the invention not limited to such an application, but basically can also be used with other types of injection systems.

Figur 1

als bevorzugtes Ausführungsbeispiel der Erfindung den Kopfbereich eines Injektors in einer Querschnittsdarstellung sowie

Figur 2

eine Detailansicht der Kontaktstelle zwischen dem Aktuator und dem Ventilkolben des in Figur 1 dargestellten Injektors im Querschnitt.

Other advantageous developments of the invention are characterized in the subclaims or are shown in more detail below together with the description of the preferred embodiment of the invention with reference to the figures. Show it:

Figure 1

as a preferred embodiment of the invention, the head area of an injector in a cross-sectional view and

Figure 2

a detailed view of the contact point between the actuator and the valve piston of the injector shown in Figure 1 in cross section.

The injector shown in Figure 1 is modular and is used to inject fuel into a combustion chamber Internal combustion engine, being at the top of the injector as a component an injector head 1 is arranged, which on the Underside seamlessly into the common injector housing 2 passes so that the essential components of the injector mechanically fixed by the common injector housing 2 become.

On the one hand, the injector head 1 enables the connection of a Injection line to the injector with a central injection system to connect that for all cylinders of the internal combustion engine provides the required injection pressure. For this purpose, the injector head 1 is chamfered on its upper side and provided with a screw connection 3 with an internal thread, which receives the end of the injection line.

On the other hand, the injector head 1 has on its underside essentially cylindrical fuselage part on which below the bevel key surfaces 4 are molded together with a circumferential cylindrical collar 5 the engagement allow a clamping claw, which for simplification not is shown. On the one hand, the clamping claw presses axially on top of the circumferential collar 5, which makes the entire injector in a corresponding location hole in the cylinder head the internal combustion engine is pressed axially downwards, wherein between the lower face of the injector and the bottom surface a copper disc is arranged in the receiving bore, to seal the location hole. On the other hand, the Clamping claw laterally into the key surfaces 4 and prevents thus a twist of the injector when assembled around its longitudinal axis.

Furthermore, the injector has a center on its top arranged cylindrical bore for receiving a Actuator 6, wherein in the lateral surface of the actuator 6 below two cylindrical circumferential grooves 7, 8 arranged one above the other are, the lower groove 8 in the assembled state receives an O-ring that the annular gap between seals the actuator 6 and the bore in the injector head 1. In the upper groove 7, however, is in the assembled state a wire ring is arranged, the fastening via a banjo bolt of the actuator 6 in the injector head 1. The actuator 6 allows axial in a conventional manner Actuating movement to control fuel injection. The Actuator 6 acts here without the conventional injectors used mechanical links directly to one Valve piston 9. On the one hand, this offers the advantage that a component can be dispensed with, which means that the manufacturing and Assembly effort is reduced. On the other hand it will the life and reliability of the injector increases because the conventionally used transmission levers in terms the lifetime are problematic.

The contact surface between the lower end face of the actuator 6 and the upper end face of the valve piston 9 essential in comparison to conventional injectors larger, which has the advantage that even when switching of the injector a film of liquid between the actuator 6 and the valve piston 9 remains, whereby a hydraulic Match compensation takes place. The lower face of the Actuator 6 is slightly convex, as shown in the figure 2 can be seen. This will tear off the liquid film due to those occurring during a switching operation mechanical loads on the contact surface between the Actuator 6 and the valve piston 9 prevented. Alternatively can also the upper end face of the valve piston 9 accordingly be convex.

In addition, there is between the actuator 6 and the valve piston 9 a spring 10 is arranged, the actuator 6 and Valve piston 9 axially apart and thus at rest of the injector restores full axial play compensation. In addition, the spring 10 also allows compensation of thermal expansion of the individual components.

A separate valve housing is used to guide the valve piston 9 11 inserted into the injector housing 2, which is the advantage offers that the valve seat to be hardened for the valve piston 9 in the valve housing 11 and not in the common Injector housing 2 is located, so that a complex heat treatment of the entire injector housing 2 for hardening the Valve seat can be dispensed with and only a hardening of the Valve housing 11 is required, which is much less is complex.

A control unit is also located below the valve piston 9 12 arranged with a servo valve, the actuator 6 actuated the servo valve via the valve piston 9 and thus indirectly the position of a nozzle needle 21 in the guide bore 20 a nozzle 13 and thus controls the fuel flow, of the injector into the combustion chamber via a nozzle 13 Internal combustion engine is injected. The nozzle 13 is in the Drawing only shown schematically and can with the injector housing 2 connected via a conventional clamping nut are not shown in the drawing in order to maintain clarity.

Finally, the injector shown has a special one advantageous form of leakage return on by instead one essentially over the entire length of the injector continuous additional leakage line an already existing central bore 14 in which a piston 22 axially is slidably arranged, which acts on the nozzle needle 21, is used for the leakage return line. hereby the manufacturing cost of the illustrated invention Injector further reduced. The injector shown also has an axially extending leakage line 15 on, but this only extends from above to below the control unit 12, where the leakage line 15 then into the central bore 14 opens. The connection of the leakage line 15 with the central bore 14 takes place here a radial bore 16 located at the mouth of the Leakage line 15 from the outer surface of the injector housing 2 extends inwards to the central bore 14, wherein the leakage line 15 is cut to the entry of leakage fluid from the central bore Allow 14 in the leakage line 15. Such a radially from the lateral surface of the injector housing 2 internal bore 16 does require sealing the outer mouth opening by a ball 17, however manufacturing technology much easier than other constructive Possibilities of the leakage line 15 in the central To let bore 14 open.

When assembling the injector, the control unit 12 is also used the servo valve, the valve housing 11 and the valve piston 9 pushed into the injector housing 2. Then then the axial position of the valve piston 9 relative to the actuator 6 set by the length of the valve piston 9 for example is adjusted by measuring and grinding.

Claims (9)

1. Injector for an injection unit of an internal combustion engine, with an injector head (1), a nozzle (13) to inject fuel into the combustion chamber of the internal combustion engine, a control unit (12) to control the passage of fuel from the injector head (1) to the nozzle (13) and an actuator (6) for the mechanical activation of the control unit (12) to control fuel injection, whereby at the injector head (1) an injector housing (2) comprises a single part, which holds the control unit (12) as a minimum and whereby the actuator (6) acts directly on a valve piston (9), characterised in that the contact surface between the actuator (6) and the valve piston (9) is so large that a fluid film remains between the contact surfaces of the actuator (6) and the valve piston (9) during a switching process.
2. Injector according to Claim 1, characterised in that the surfaces of the actuator (6) and/or the valve piston (9) facing each other are slightly convex in form, to prevent removal of the fluid film.
3. Injector according to one of the preceding claims, characterised in that a spring (10) is mounted between the actuator (6) and the valve piston (9).
4. Injector according to one of the preceding claims, characterised in that the valve piston (9) is mounted in a separate valve housing (11) inside the injector housing (2), so that thermal treatment of the injector housing (2) otherwise required to harden the valve seat becomes superfluous.
5. Injector according to one of the preceding claims, characterised in that a circumferential collar (5) is formed externally on the sleeve surface of the injector housing (2), which collar (5) is used as a base for a tensioning claw, to hold the injector axially in a recess in the cylinder head of the internal combustion engine.
6. Injector according to one of the preceding claims, characterised in that key surfaces (4) are formed externally on the sleeve surface of the injector housing (2) to engage a tensioning claw, to prevent twisting of the injector when assembled.
7. Injector according to one of the preceding claims, characterised in that an essentially axial leakage line (15) is provided, which discharges below the control unit (12) into a centric hole (14), which is used to hold a control bar and for return leakage.
8. Injector according to Claim 7, characterised in that an essentially radial hole (16) is located in the injector housing (2), which runs from outside to the centric hole (14) at the discharge point of the leakage line (14), to connect the leakage line (15) to the centric hole (14), whereby the external discharge opening of the radial hole (16) is closed when assembled.
9. Injector according to Claim 8, characterised in that the external discharge opening of the radial hole (16) is closed by a sphere (17) when assembled.

Images