EP1891322A1

EP1891322A1 - Common rail injector

Info

Publication number: EP1891322A1
Application number: EP06743255A
Authority: EP
Inventors: Hans-Christoph Magel
Original assignee: Robert Bosch GmbH
Current assignee: Robert Bosch GmbH
Priority date: 2005-06-01
Filing date: 2006-04-06
Publication date: 2008-02-27
Also published as: WO2006128754A1; DE102005025133A1

Abstract

The invention relates to a common rail injector having an injector housing (1) which has a fuel supply line (26) which is connected to a pressure space (17, 22) within the injector housing (1), fuel from said pressure space (17) being injected, as a function of the pressure in a coupling space (35, 39, 41), into a combustion chamber of an internal combustion engine when a nozzle needle (8) lifts up from its seat, the coupling space (35, 39, 41) being delimited by that end of the nozzle needle (8) which is remote from the combustion chamber and by that end of an actuator (30), piezoelectric actuator, which is close to the combustion chamber. In order to reduce the length of the actuator, the nozzle needle (8) is guided in a transformer piston (52) which delimits the coupling space (35, 39, 41) and, in a first nozzle opening phase, is moveable relative to a transformer piston stop (3) with which the transformer piston (52) comes into contact in a second nozzle opening phase.

Description

ROBERT BOSCH GMBH R. 311039

70442 STUTTGART

Common rail injector

description

The invention relates to a common rail Inj ector with an injector, which has a Kraftstoffzu- running, which communicates with a central fuel high pressure source outside of the injector and with a pressure chamber inside the injector in connection from which, depending on the pressure in a Coupling space is injected with high pressure fuel into a combustion chamber of an internal combustion engine, when a nozzle needle lifts from its seat, the coupling space from the combustion chamber remote end of the nozzle needle and the combustion chamber near the end of an actuator, in particular a piezoelectric actuator, or at the combustion chamber near end The actuator attached coupler piston is limited.

State of the art

If the coupling space is limited by an actuator, in particular a piezoelectric actuator, or by a coupling piston attached to the end of the actuator close to the combustion chamber, this is also referred to as a direct nozzle needle control. The object of the invention is to provide a common rail injector according to the preamble of claim 1, in which the actuator ensures the necessary nozzle needle stroke with a shorter actuator length than conventional common rail injectors.

Advantages of the invention

The object is with a common rail injector with an injector housing, which has a fuel inlet, which communicates with a central high-pressure fuel source outside the injector housing and with a pressure chamber inside the injector housing, from which, depending on the pressure in a coupling space, injected high pressure fuel is injected into a combustion chamber of an internal combustion engine when a nozzle needle lifts from its seat, the coupling space of the combustion chamber remote end of Düsenna- del and the combustion chamber near the end of an actuator, in particular a piezoelectric actuator, or at the combustion chamber near the end of the actuator attached coupler piston is limited, achieved in that the nozzle needle is guided in a booster piston which limits the coupling space and which is movable in a first nozzle needle opening phase relative to a Ü bersetzerkolbenanschlag on which the booster piston in a second Düsennadelöf The starting phase comes to an end. In the context of the present invention, direct control of the pressure in the coupling space is understood to mean the generation of a pressure drop and / or a pressure rise as a consequence of a change in volume, in particular a change in length, of the actuator. Of the Coupling space is limited by an end face of the actuator or coupled to the actuator or on the actuator mounted coupler piston, which is also referred to as an actuator head. The volume of fuel contained in the coupling space allows the compensation of thermal expansion and manufacturing tolerances. The coupling space, which is partially limited by the booster piston, permits variable hydraulic transmission between the actuator or a coupler piston attached to the end of the actuator close to the combustion chamber and the nozzle needle. In the first nozzle needle opening phase, the hydraulic ratio between the actuator and the nozzle needle by the ratio of the hydraulic coupling space limiting surface of the actuator or attached to the combustion chamber near end of the actuator coupler piston to the sum of the hydraulic coupling space defining surfaces of the nozzle needle and the Translator piston defined. This transmission ratio is preferably designed for a large nozzle nozzle opening force in the first nozzle needle opening phase. After the first nozzle needle opening phase, the booster piston abuts the transfer spool stopper. The booster piston stop limits the stroke of the booster piston. In the second nozzle needle opening phase, the booster piston stops moving. Thus, the hydraulic ratio between the actuator and the nozzle needle in the second nozzle needle opening phase by the ratio of the hydraulic coupling space limiting surface of the actuator or attached to the combustion chamber near end of the actuator coupler piston to the hydraulic coupling - A -

Defined space limiting surface of the nozzle needle. Since the necessary nozzle needle opening force has then already greatly decreased, the transmission ratio in the second nozzle needle opening phase is preferably designed for a complete needle opening with a small Aktorhub. By the translator piston can be ensured with a relatively small actuator length both a large nozzle needle opening force at the beginning of the injection and a sufficient Düsennadelhub.

A preferred embodiment of the common rail injector is characterized in that the booster piston has substantially the shape of a sleeve which is movable in the axial direction relative to the nozzle needle. Preferably, the sleeve has the shape of a hollow circular cylinder whose inner diameter is ground to the outer diameter of the nozzle needle.

Another preferred embodiment of the common rail injector is characterized in that a collar is provided at the combustion chamber remote end of the nozzle needle. The collar is preferably formed integrally with the nozzle needle. But for assembly purposes, the federal government can also be formed by a separate component which is releasably attached to the nozzle needle. The federal government forms a stop for the booster piston.

A further preferred embodiment of the common rail injector is characterized in that between the collar and the booster piston an adjusting ring is clamped or arranged. By the adjusting ring, the distance between the Ü bersetzerkolben and the booster piston stop in the first nozzle needle opening phase can be adjusted.

Another preferred embodiment of the common rail injector is characterized in that the nozzle needle has a spring plate which forms an abutment for a spring device which is clamped or arranged between the spring plate and the booster piston. The spring device may be the same spring device by which the nozzle needle is biased into its closed position. But it can also be used an additional spring device.

A further preferred exemplary embodiment of the common rail injector is characterized in that the injector housing comprises a nozzle body in which the nozzle needle is accommodated and an injector body in which the actuator is accommodated, wherein an intermediate body is arranged between the injector body and the nozzle body which has or forms the stop for the booster piston. As a result, the production of the injector according to the invention is simplified.

A further preferred embodiment of the common rail injector is characterized in that the coupling space comprises an actuator pressure chamber, which is delimited radially outwardly by an actuator dumping space limiting sleeve which is located at the end of the actuator close to the combustion chamber or at the combustion chamber. near the end of the actuator mounted coupler piston is guided back and forth movable. Preferably, the piezoelectric actuator is constantly energized. When the piezoelectric actuator is relieved of pressure, the pressure in the coupling space drops, so that the nozzle needle lifts from its seat and releases at least one injection hole, is injected by the high-pressure fuel into the combustion chamber of the internal combustion engine.

A further preferred exemplary embodiment of the common rail injector is characterized in that the coupling space comprises a nozzle needle control chamber, which is delimited radially outwardly by a nozzle needle control chamber limiting sleeve which is guided to and fro movable at the combustion chamber distal end of the nozzle needle. The limited in the radial direction of the Düsennadelsteuerraumbegrenzungshülse Düsennadelsteuerraum is limited in the axial direction by the combustion chamber remote end face of the nozzle needle and the combustion chamber remote end face of the booster piston.

A further preferred embodiment of the common rail injector is characterized in that the booster piston is guided in the radial direction between the nozzle needle and the Düsennadelsteuerraum- limiting sleeve. Alternatively, the booster piston may also be guided between the nozzle needle and the injector housing.

Further advantages, features and details of the invention will become apparent from the following description in which, with reference to the drawing tion various embodiments are described in detail. The features mentioned in the claims and in the description may each be essential to the invention individually or in any combination.

drawing

Show it:

Figure 1 shows a first embodiment of a common rail injector according to the invention in longitudinal section and

Figure 2 shows a second embodiment of a common rail injector according to the invention in longitudinal section.

Description of the embodiments

1 shows a first embodiment of a common rail injector according to the invention is shown schematically in longitudinal section. The illustrated common rail injector has an injector housing, generally designated 1. The injector housing 1 comprises a nozzle body 2, which projects with its lower free end into the combustion chamber of an internal combustion engine to be supplied. With its upper, combustion chamber remote end face of the nozzle body 2 is clamped by means of a (not shown) clamping nut a- xial against an intermediate body 3 and an injector 4. In the nozzle body 2, an axial guide bore 6 is recessed, in which a nozzle needle 8 is guided axially displaceable. At the tip 9 of the nozzle needle 8, a sealing edge 10 is formed, which cooperates with a sealing seat or with a sealing surface 11 which is formed on the nozzle body 3. If the tip 9 of the nozzle needle 8 with its sealing edge 10 is in contact with the sealing seat 11, injection holes 13 and 14 in the nozzle body 2 are closed. When the nozzle needle tip 9 lifts off from its sealing seat with the sealing edge 10, high-pressure fuel is injected through the injection holes 13 and 14 into the combustion chamber of the internal combustion engine.

Starting from the tip 9, the nozzle needle 8 has a pressure chamber portion 15, which is formed substantially circular cylindrical. The pressure space section 15 is followed by a truncated section 16, which is also referred to as a pressure shoulder. The sections 15 and 16 are, at least partially, arranged in a pressure chamber 17 which is formed between the nozzle needle 8 and the nozzle body 2.

The truncated cone-like widening section 16 is followed by a substantially circular-cylindrical guide section 18. The guide section 18 is guided in the axial guide bore 6 of the nozzle body 2 so as to be movable back and forth. By flats 19, 20, which are formed on the guide portion 18, a fluid connection between the pressure chamber 17 and another pressure chamber 22 created, which is also referred to as a nozzle spring chamber and is provided in the combustion chamber remote end of the nozzle body 2.

The nozzle spring chamber 22 communicates with an actuator chamber 25 in the injector body 4 via a connecting channel (not shown) formed in the intermediate body 3. The actuator chamber 25 in turn is connected via an inlet channel 26 to a high-pressure fuel accumulator 28, which is also referred to as a common rail.

In the actuator chamber 25, a piezoelectric actuator 35 is arranged, at the end remote from the combustion chamber an actuator base 31 is mounted, which rests in a sealing manner on the injector 4. The injector body 4 is preferably designed in several parts.

At its end close to the combustion chamber, a piezoactuator head 32, which is also referred to as a coupler piston, is attached to the piezoactuator 30. The piezoelectric actuator head 32 essentially has the shape of a straight circular cylinder, at whose end close to the combustion chamber an actuator pressure chamber limiting sleeve 34 is guided so as to be movable back and forth. Sufficient play is provided between the actuator pressure chamber limiting sleeve 34 and the actuator head 32, so that high-pressure fuel passes into an actuator pressure chamber 35, which is delimited in the radial direction by the actuator pressure chamber limiting sleeve 34. The piezoelectric actuator 30 is powered by electrical connections 33 with electricity. At the combustion chamber remote end of the actuator head 32, a collar 36 is formed. A helical compression spring 37 is clamped between the collar 36 and the end of the actuator pressure chamber limiting sleeve 34 remote from the combustion chamber, by means of which a biting edge 38 provided at the end of the actuator pressure chamber limiting sleeve near the combustion chamber is pressed against the intermediate body 3 in a sealing manner. In the axial direction, the actuator pressure space 35 is delimited by the actuator head 32 and the intermediate body 3.

In the intermediate body 3, a through hole 39 is recessed which connects the actuator pressure chamber 35 with a nozzle needle control chamber 41, which is delimited in the radial direction by a nozzle needle control chamber limiting sleeve 42. The Düsennadelsteuerraumbe- grenzungshülse 42 has at its combustion chamber remote end a biting edge 43 which bears in a sealing manner on the intermediate body 3.

The nozzle needle 8 has at its tip 9 opposite end on a circular cylindrical end portion 45. The end section 45 is bordered by a collar 44 at its end remote from the combustion chamber. At its combustion chamber near end of the end portion 45 is bounded by another collar 46, which is also referred to as a spring plate. The spring plate 46 forms a contact surface for one end of a nozzle needle spring 47, which is clamped between the spring plate 46 and the nozzle needle control chamber limiting sleeve 42. The biasing force of the nozzle needle spring 47 causes the Düsennadelsteu- space limiting sleeve 42 is held with its biting edge 43 into contact with the intermediate body 3. Au- In addition, the nozzle needle spring 47 causes the tip 9 of the nozzle needle 8 with the sealing edge 10 to be held in abutment against the associated seal seat 11.

The actuator pressure space 35, the through-hole 39 and the nozzle needle control space 41 together form a coupling space filled with pressurized fuel. Between the end portion 45 of the nozzle needle 8 and the Düsennadelsteuerraumbegren- tion sleeve 42, a booster piston 52 is guided in the axial direction to move back and forth. The transfer piston 52 has the shape of a hollow circular cylinder and is biased by a booster piston spring 54 away from the combustion chamber. In the axial direction, an adjusting ring 56 is arranged between the booster piston 52 and the collar 44. By the adjustment ring 56 of the booster piston 52 is held at a preselected distance to the collar 44. The outer diameter of the booster piston 52 is slightly larger than the inner diameter of the through hole 39 in the intermediate body 3. By the adjusting ring 56, a stroke 58 can be adjusted, which the booster piston 52 can perform before it comes to the intermediate body 3 into abutment. The intermediate body 3 forms a Hubbegrenzungsanschlag for the booster piston 52nd

The nozzle needle 8 together with the translation piston 52 delimits the coupling space in the axial direction. The booster piston 52 is axially slidably ground on the nozzle needle 8. The coupling space is sealed off from the nozzle spring chamber 22 by the nozzle needle control chamber limiting sleeve 42. tet. The booster piston 52 is biased by the booster piston spring 54 to its rest position. About the adjustment ring 56 of the booster piston 52 is coupled to the collar 44 of the nozzle needle 8 and has to the intermediate body 3 of the injector 1 to the stroke distance 58. About the adjustment ring 56, which is also referred to as a dial, the stroke 58 of the booster piston 52 can be adjusted.

In the rest state prevails in the coupling space 35, 39, 41 rail pressure. The nozzle needle 8 is closed. The piezoelectric actuator 30 is charged at rest and has its maximum length. To actuate the injector, the piezoactuator 30 is discharged, thereby pulling the coupler piston 32 back. Then the pressure drops in the coupler space 35, 39, 41. The nozzle needle 8 begins to open. In this phase, which is also referred to as the first nozzle needle opening phase, a ratio between the actuator 30 and the nozzle needle 8 acts according to the area ratio (in the coupling space 35, 39, 41) of the end face of the coupler piston 32 near the combustion chamber to the sum of the combustion chamber distant End faces of the nozzle needle 8 and the booster piston 52. This area ratio is designed for the large initial needle opening force.

In the first nozzle needle opening phase, the nozzle needle 8 and the booster piston 52 move upwards away from the combustion chamber. The movement of the booster piston 52 is interrupted as soon as the booster piston 52 comes into abutment against the intermediate body 3. This phase is also called second nozzle needle opening phase called. In the second Düsenna- delöffnungsphase acts between the actuator 30 and the nozzle needle 8, a translation according to the area ratio of the combustion chamber near end face of the coupler piston 32 to the combustion chamber remote end face of the nozzle needle 8. Since the necessary needle opening force has now been greatly reduced, preferably a gear ratio is selected here , which allows a complete needle opening with a small actuator stroke.

Thus, according to the present invention, both a high needle opening force at the beginning and a sufficient needle lift for injection can be realized with a small piezoactuator. In both nozzle needle opening phases, the transmission ratio of actuator to nozzle needle can be optimally adapted to the requirements of the needle control. This makes it possible to realize a direct needle control with the smallest possible actuator.

To close the nozzle needle 8, the actuator 30 is loaded again, wherein it expands. Then results in the coupling space 35, 39, 41, an overpressure, which acts on the combustion chamber remote end face of the nozzle needle 8. This causes the nozzle needle 8 closes quickly. In this case, the booster piston 52 is initially held by the booster piston spring 54 above and then taken by the downward movement of the nozzle needle 8, more precisely from the collar 44 of the nozzle needle 8, with the interposition of the adjusting ring 56. Due to the construction according to the invention with only one hydraulic coupling space 35, 39, 41 between the piezoelectric actuator 30 and the nozzle needle 8, a rigid transmission behavior can be achieved despite a variable hydraulic transmission, whereby the switching performance is improved. The filling of the coupling space 35, 39, 41, which is also referred to as a coupler space, can take place, for example, via a corresponding gap flow or by throttling. In order to ensure a good mountability of the booster piston 52 and the adjusting ring 56 on the nozzle needle 8, either the spring plate 46 or the collar 44 on the nozzle needle 8 is designed to be removable.

2 shows a further embodiment of a common rail injector according to the invention is shown schematically in longitudinal section. To denote the same parts, the same reference numerals as in Figure 1 are used. To avoid repetition, reference is made to the preceding description of FIG. In the following, only the differences between the two embodiments will be discussed.

In the embodiment shown in Figure 2, in addition to a through hole 62 connecting channels 23 and 24 are indicated in the intermediate body 3 and the nozzle body 2, via which a flow connection between the nozzle spring chamber 22 and the actuator chamber 25 is provided. In addition, omitted in the embodiment shown in Figure 2, the Düsennadelsteuerraumbegrenzungshülse (42 in Figure 1). In the illustrated in Figure 2 Embodiment, a booster piston 65 is guided directly in the nozzle body 2. As a result, the required number of individual parts can be reduced. Between the collar 44 and the booster piston 65, an adjustment ring 66 is arranged. The booster piston 65 and the adjusting ring 66 are biased by the nozzle needle spring 47 against the collar 44. The hydraulic function of the injector shown in FIG. 2 corresponds to the injector illustrated in FIG.

Claims

R. 311039Patentansprüche

A common rail injector having an injector housing (1) having a fuel inlet (26) connected to a central fuel high pressure source (28) outside the injector housing (1) and having a pressure space (17, 22) within the injector housing

(1) is in communication, from which, depending on the pressure in a coupling space (35,39,41), high-pressure fuel in a

Combustion chamber of an internal combustion engine is injected when a nozzle needle (8) lifts from its seat, the coupling space (35,39,41) from the combustion chamber remote end of the nozzle needle (8) and the combustion chamber near the end of an actuator (30), in particular a piezoelectric actuator, or a coupling piston (32) attached to the end of the actuator close to the combustion chamber, characterized in that the nozzle needle (8) is guided in a booster piston (52; 65) which delimits the coupling space (35, 39, 41) and which is in a first nozzle needle opening phase is movable relative to a booster piston stop (3) on which the booster piston (52; 65) comes into abutment in a second nozzle needle opening phase.

2. Common rail injector according to claim 1, characterized in that the booster piston (52; 65) has substantially the shape of a sleeve which is movable in the axial direction relative to the nozzle needle (8).

3. Common-rail injector according to one of the preceding claims, characterized in that at the combustion chamber remote end of the nozzle needle (8) a covenant

(44) is provided.

4. Common rail injector according to claim 3, characterized in that between the collar (44) and the booster piston (52; 65) an adjusting ring (56; 66) is clamped.

5. Common rail injector according to one of the preceding claims, characterized in that the nozzle needle (8) has a spring plate (46) which forms an abutment for a spring device (54; 47) between the spring plate (46) and the translator piston (52; 65) is clamped.

6. Common rail injector according to one of the preceding claims, characterized in that the injector housing (1) comprises a nozzle body (2), in which the nozzle needle (8) is accommodated, and an injector body (4), in which the actuator (30) is accommodated, wherein between the injector body (4) and the nozzle body (2) an intermediate body (3) is arranged, which has the stop for the booster piston (52, 65).

7. Common rail injector according to one of the preceding claims, characterized in that the coupling space comprises a Aktordruckraum (35) which is bounded radially outwardly by a Aktordruckraumbegren- tion sleeve (34) at the combustion chamber near the end of the actuator ( 30) or one at the near the end of the actuator mounted coupler piston (32) is guided back and forth movable.

8. Common rail injector according to one of the preceding claims, characterized in that the

Coupling space a nozzle needle control chamber (41) summarizes, which is bounded radially outwardly by a Düsennadelsteu- erraumbegrenzungshülse (42), which is guided to the combustion chamber remote end of the nozzle needle (8) reciprocally movable.

9. common rail injector according to claim 8, characterized in that the booster piston (52) between the nozzle needle (8) and the Düsennadelsteuer- space limiting sleeve (42) is guided.