EP1283955B1 - Extended pump-valve-nozzle unit having hydraulic-mechanical translation - Google Patents

Description

Technical field

The present invention relates to a pump-valve-nozzle unit (PVD) in a stretched arrangement with hydraulic-mechanical transmission.

The design of today's internal combustion engines, on which up to four valves can be provided per cylinder, considerably limits the space available for injection systems in the cylinder head. Hydraulic mechanical translators are also assigned to the PVD units, which also have to be accommodated.

State of the art

DE 39 10 793 A1 relates to a fuel injection device for diesel internal combustion engines with at least one pump piston. This is sealingly guided in a sleeve and, together with the pump body, forms a delivery chamber which is connected to a suction chamber by a control element during the downward movement of the pump piston, the delivery chamber being in flow communication with an injection valve via an injection line. The invention has for its object to keep the harmful space of the fuel injector as small as possible in order to be able to achieve high injection pressures. This is achieved in that there is a permanently open flow connection between the delivery chamber and the injection valve.

DE 198 09 627 A1 relates to a fuel injection device for internal combustion engines. This includes a high-pressure fuel pump which is connected on the suction side to a low-pressure fuel supply system and on the high pressure side to a fuel injection valve which projects into the combustion chamber in the internal combustion engine. The high-pressure delivery in a high-pressure channel provided between the high-pressure fuel pump and the fuel injection valve can be controlled by means of an electrical control valve, which has an electrically actuatable, displaceable valve member with a valve sealing surface. With the valve sealing surface, it interacts with a stationary valve seat to form a sealing cross section. In order to improve the operating times and susceptibility to wear of the control valve, the control valve member and / or a sleeve guiding it are made of ceramic.

In the arrangements of fuel injection devices discussed in the prior art, the L-shaped arrangement from the valve to the injection nozzle can lead to pressure pulsations in the system.

No. 4,782,807 shows a cam-operated pump-nozzle fuel injection device, in which a pump piston can be moved into a pump chamber, from which a bore branches off. The bore branching off from the pump work space opens at a constriction point of a valve element which can be moved by an actuator. Another bore branches off below the valve element, via which fuel flows to the nozzle part of the pump-nozzle fuel injection device according to US Pat. No. 4,782,807. The pump unit consisting of pump piston and pump working space, that this valve member, which can be actuated by the actuator, and the nozzle body according to this solution, are hydraulically connected one behind the other in relation to the fuel flow.

Presentation of the invention

With the arrangement proposed according to the invention, an essentially vertical arrangement of a pump part, a valve part adjoining this and a nozzle part of an injection arrangement adjoining the valve part can be ensured. With this essentially vertical arrangement of the components PVD, a largely flow-free pressure build-up can be achieved. According to this arrangement, the components PVD are hydraulically seen, all in a row. The straight arrangement of the PVD units allows one Flange on the side of a hydraulic-mechanical translator. Due to the essentially vertical arrangement of the pump part, valve part and nozzle part, an aspect ratio between the pump chamber and the control valve chamber and the control valve chamber to the nozzle chamber of 1: 5 can be optimally realized between these parts. This allows avoid long injection lines; rather, the time constant of an injection is now significantly larger compared to the time of the wave propagation between the individual elements, such as the nozzle space. This leads to the fact that the pronounced pressure fluctuations which occur in the arrangements of the PVE units according to the solutions from the prior art can be suppressed between the components pump part, valve part and nozzle part in the solution according to the invention. The negative effects of such pressure pulsations in overly long lines under high pressure can lead to undesirable phenomena, such as undefined opening, flying or closing of a nozzle needle opening above the pressure, which in extreme cases leads to unstable needle opening behavior and re-closing nozzle needles, depending on the speed of the cam driving the pump body can lead.

With a pump-valve-nozzle unit arranged according to the present invention, these disadvantages can be avoided by means of an inlet bore system which is designed in optimal length ratios. Due to the elongated arrangement of the pump part, valve part and the nozzle part, installation space can also be saved in an optimal manner, so that there is sufficient installation space per cylinder of an internal combustion engine for the provision of two high-pressure injection valves, even if these are equipped with piezo actuators flanged on the side for actuating the control valve attached hydraulic-mechanical translator are provided.

Since an additional mechanical transmission is provided on the piezo actuator, the valve chamber can be designed in an optimal manner with regard to the aspect ratios of the line systems. By flange-mounting the hydraulic-mechanical translator on the side, the mechanical stroke paths required to actuate the control valve can be easily adjusted. Since the actuating unit contains a mechanical transmission in the form of a lever which can be pivoted about an axis of rotation, the hydraulic Translation volume can be kept small, which can be operated with very low pressures (only 6 bar).

In addition, the vertical arrangement of the PVE units of an injector proposed according to the invention is accompanied by the advantage that, instead of the three to four high-pressure bore intersections in the injector body previously required, only two high-pressure bore intersections in the injector body are now necessary. In order to ensure a pressure threshold strength of up to approx. 2000 bar of an injector body for high-pressure diesel injection systems, the high-pressure bore intersections must be minimized, since these impair the mechanical strength of the injector body. The high-pressure bore intersections define the limit of the mechanical stress on an injector body, which limits the pressure level that can be achieved in the high-pressure collecting space (common rail).

drawing

The invention is explained in more detail below with the aid of the drawing.

Figur 1

die aus bisherigen Lösungen bekannten Y- bzw. L-förmig verlaufenden P-V-D-Teilsysteme eines Einspritzsystemes,

Figur 2

die erfindungsgemäß vorgeschlagene Anordnung der Komponenten eines Pumpen-Ventil-Düse-Systemes eines Injektors,

Figur 3

den hinsichtlich des Druckschwingungsaufbaus optimalen Leitungslängenverhältnisse der den Pumpenraum, die Ventileinheit bzw. den Düsenteil miteinander verbindenden Kraftstoffzuleitungen eines Einspritzsystemes und

Figur 4

eine Ausführungsvariante der erfindungsgemäß vorgeschlagenen PVD-Einheit mit zeitlich im Bereich des Ventilteiles angeflanschten hydraulisch-mechanischem Übersetzer.

It shows:

Figure 1

the Y or L-shaped PVD subsystems of an injection system known from previous solutions,

Figure 2

the arrangement according to the invention of the components of a pump-valve-nozzle system of an injector,

Figure 3

the optimal line length ratios of the fuel supply lines of an injection system connecting the pump chamber, the valve unit and the nozzle part with respect to the pressure oscillation structure and

Figure 4

An embodiment variant of the PVD unit proposed according to the invention with a hydraulic-mechanical translator flanged in time in the area of the valve part.

variants

FIG. 1 shows the Y or L-shaped arrangements of the components which have arisen in previous solutions on PVD systems.

From the standpoint of the hydraulic design with regard to the susceptibility of a PVD system with regard to pressure oscillation build-up, a vertical arrangement of the pump part, the valve part, and the nozzle part of an injection system is desirable. The valve chamber must not be connected in parallel to the pump chamber. Furthermore, the injector arrangements shown schematically in FIG. 1 in the area of the cylinder head of an internal combustion engine require considerable installation space, which is becoming increasingly scarce as the four-valve technology progresses.

FIG. 2 schematically shows the arrangement of the components of a pump-valve-nozzle system of an injector proposed according to the invention.

The essential components of the fuel injection device 1 are arranged in the vertical direction. With regard to the fluid direction of the fuel coming from the pump part P under high fuel, the components P, V and D are hydraulically arranged one behind the other. With this configuration, on the one hand, construction space is saved, which is only very scarce available on the cylinder head of an internal combustion engine, and the supply line connecting the individual parts P, V and D of the fuel injection device can be designed in the optimum length. This is an optimal behavior with regard to the build-up of pressure fluctuations of the fuel under high pressure in the Supply lines can be achieved if the length ratio of the supply lines 5 or 8, ie ₁ : 1 _{2 is} in the range between 1: 4 and 1: 6. The length ratio of the two inlet bores 5 and 8 (cf. illustration according to FIG. 3) is preferably 1: 5. This selected length ratio of the inlet and connection lines between the components of the pump-valve-nozzle system of a fuel injection device 1 a largely vibration-free pressure build-up in the fuel injection device 1 can be achieved. Vibration-free pressure build-up within a pump-valve-nozzle system offers the possibility, in further development of the injection systems, to achieve a boat pre-injection, which is very difficult to achieve in the injection system which is subject to considerable pressure pulsations, the precision of the pre-injection or Boat quantities left something to be desired

The illustration according to FIG. 3 shows the optimal spacing relationships of the pump part, valve part and nozzle part of a fuel injection device with regard to the pressure oscillation structure.

According to the illustration in FIG. 3, the pump part P, consisting of the pump piston 3, which dips into the pump chamber 4, is connected to the valve chamber 6.1 via the inlet bore 5. The length of the inlet bore 5 connecting the pump chamber 4 to the valve chamber 6.1 is denoted by l ₁ . The inlet bore 8 extends from the valve chamber 6.1 through the injector body to the nozzle chamber, denoted by reference numeral 12. The length of the axial extension of the inlet bore 8 between the valve chamber 6.1 and the nozzle chamber 12 of the injector body is denoted by l ₂ . According to the explanations in connection with the illustration according to FIG. 2, the ratio of the lengths l ₁ , l ₂ of the inlet bore 5 to the inlet bore 8 is advantageously in the range between 1: 4 and 1: 6, the length ratio l is preferably ₁ : l ₂ , 1: 5. With these length ratios of the inlet bores 5 and 8 in the interior of the injector body of the fuel injection device 1, the structure of Avoid pressure pulsations in the high pressure fuel fluid effectively.

4 shows an embodiment variant of the PVD unit proposed according to the invention with hydraulic, mechanical translators flanged to the side in the area of the valve part V.

The injector 1 contains in its upper region a pump part P. This receives a pump piston 3 provided coaxially to the line of symmetry of the injector body 1 in a bore 2, which is acted upon by a cover together with a compression spring enclosed by the cover. The pump piston 3 plunges into a pump chamber 4 and in this way pressurizes an existing fuel supply there. A bore 5 extends from the pump chamber 4 into a valve chamber 6.1 of a control valve 6, which is received in a valve part V of the injector of the fuel injection device 1.

The length of the inlet bore 5 between the pump chamber 4 and the valve chamber 6.1 is denoted by I ₁ . The control part 6, which is enclosed in the area of the inlet bore 5 by the pump chamber 4 and the inlet bore 8 to the nozzle chamber 12 by a valve chamber 6.1, is enclosed by a return spring 6.2, which rests on a stop face 6.3 with one end and the other end on a bore wall rests inside the injector body. The control part 6 closes the connection between the inlet bores 5 and 8 with the seat surface 6.5. A push rod 6.4 is also formed on the control part 6, the rounded head of which protrudes laterally from the injector body 1. In the position of the control part 6 shown in FIG. 4, it is in the closed position 6.6 by resting the seat surface 6.5 on the edge of the valve space 6.1.
From the valve chamber 6.1 of the valve part V, an inlet bore 8 extends, which runs essentially parallel to the axis of symmetry of the valve body 1, to the nozzle chamber 12. The nozzle chamber 12 is penetrated by a nozzle needle 11, the nozzle seat 13 of which is formed at the tip of the injector body 1 and one Nozzle opening 14, which projects into the combustion chamber of an internal combustion engine, either closes or releases it. Above the nozzle needle 11, a pressure piece 10 is reproduced, which can be acted upon by a plate with a compression spring 9, which is completely enclosed by the injector body housing. The nozzle part D of the fuel injection device is located at a distance l ₂ from the valve part of the pump-valve-nozzle unit of the fuel injection device 1. The ratio of the lengths l _{1 of} the inlet bore 5 to the length of the inlet bore 8 between the valve chamber 6.1 of the valve part V and the Nozzle space 12 of the nozzle part D is advantageously essentially 1: 5 in accordance with the explanations given above.

To make it easier to connect the nozzle part D to the other components of the fuel injection device 1, the nozzle part D is connected to the injector body 1 by means of a screw connection 15. The centering of the nozzle part D to ensure the alignment of the inlet bore 8 in the nozzle chamber 12 is made possible by the centering pin 16 or 17, which are provided between the components to be assembled with one another.

A translator flange 7 is arranged on the side surface of the injector, in which a translator lever 18 which can be pivoted about an axis is received. The translator lever 18 is acted upon on the one hand by a return spring 19 and, on the other hand, is connected with its lower end to the rounded end of the push rod 6.4 of the control part 6. The rotatably mounted translator lever 18 is moved about its pivot point via the secondary piston 20 provided in the flange 7, 27. The secondary piston 20 is connected via a gap-shaped connection through the booster flange 27 to a leak oil reservoir 22 which can be acted upon by a primary piston 23 and which results in actuation of the secondary piston 20. Above the primary piston 23, a contact plate 24 is provided, which in turn can be actuated via a piezo actuator 25. The piezo actuator 25 is screwed to the translator flange 27 on an actuator screw connection 26. Through the Lever ratios on the transmission lever 18 in relation to the force introduction point through the primary piston 20 and in relation to the push rod 6.4 for actuating the control part 6, which represent an additional mechanical translation, the hydraulic translation volume can be kept low, which means that the refill via the leakage oil pressure with small pressures , for example 6 bar can be driven. The mechanical wear that occurs between components 20, 18 and 6.4 of the valve actuation can be very easily compensated for via the leakage gap between primary piston 23 and secondary piston 20 by means of a trailing volume.

With this solution, high-pressure bore intersections in the injector body can be avoided and reduced to the number of two, as a result of which a weakening of the injector body of the fuel injection device 1 can be reduced to a minimum. The injector body of the fuel injection device according to FIG. 4 has a pressure threshold strength of pressures of up to at least 2000 bar and advantageously avoids a further high-pressure sealing surface by integrating the compression spring 9 acting on the nozzle needle 11. Sealing surfaces represent potential weak points at the pressures of 2000 bar and more required in injection systems and should therefore be avoided wherever possible.

LIST OF REFERENCE NUMBERS

1

Fuel injector

2

drilling

3

pump pistons

4

pump room

5

Inlet hole control section

6.1

valve chamber

6.2

Return spring

6.3

stop surface

6.4

pushrod

6.5

seat

6.6

closed position

7

Übersetzerflansch

8th

Inlet bore nozzle area

9

compression spring

10

Pressure piece

11

nozzle needle

12

nozzle chamber

13

nozzle seat

14

nozzle opening

15

screw

16

Centering

17

Centering

18

Transmission lever

19

Return spring

20

secondary piston

22

leakage

23

primary piston

24

Support plate

25

piezo actuator

26

Aktorverschraubung

27

flange

P

pump part

V

valve part

D

nozzle part

I ₁

Distance P-V

I ₂

Distance V-D

Claims (8)

1. Fuel injection apparatus for an internal combustion engine having an injection nozzle (14) which projects into the combustion chamber of the internal combustion engine and is connected to a valve chamber (6.1) in which a control part (6) closes and opens feed bores (5, 8) for highpressure fuel, and it is possible to actuate the control part (6) by means of a hydraulic-mechanical intensifier (18, 19, 20), a pump part (P), which comprises a pump piston (3) and a pump chamber (4), a valve part (V), which comprises a control valve (6), and a nozzle part (D), which contains a nozzle needle (11), of the fuel injection device (1) being arranged in a vertical arrangement hydraulically in series in relation to the flow of fuel, characterized in that the ratio of the lengths l₁, l₂ of the feed bores (5, 8) between the pump part (P) and the valve part (V) and between the valve part (V) and the nozzle part (D), respectively, is between 1:4 and 1:6 with respect to one another.
2. Fuel injection apparatus according to Claim 1, characterized in that the pump chamber (4), valve chamber (6.1) and nozzle chamber (12) are connected to one another via feed bores (5, 8) which extend substantially vertically.
3. Fuel injection apparatus according to Claim 2, characterized in that the length ratio l₁:l₂ of the feed bores (5, 8) is 1:5.
4. Fuel injection apparatus according to Claim 1, characterized in that the control part (6) of the valve part (V) can be actuated by a hydraulic-mechanical intensifier (18, 19, 20) which is laterally flange-connected to the fuel injection apparatus (1) in the region of the valve part (V).
5. Fuel injection apparatus according to Claim 1, characterized in that the push rod (6.4) of the control part (6) can be actuated via a pivotably mounted intensifier lever (18) counter to the effect of a restoring spring (19), and the pivoting lever (18) is moved with a secondary piston (20).
6. Fuel injection apparatus according to Claim 5, characterized in that a piezoactuator (25) acting on a primary piston (23) is accommodated at the hydraulic-mechanical intensifier (18, 19, 20 and 21), and the primary piston (23) acts hydraulically on the secondary piston (20) via a leakage gap.
7. Fuel injection apparatus according to one or more of the preceding claims, characterized in that wear to the mechanical components (6.4, 18, 20) is compensated for by additional flow of the leakage oil (22) between the intensifier pistons (20, 23).
8. Fuel injection apparatus according to Claim 1, characterized in that a compression spring (9) acting on the nozzle needle (11) in the nozzle part (D) is integrated into the injector housing of the fuel injection apparatus (1).