DE102004046899A1 - Fuel injector - Google Patents

Abstract

A fuel injector (1) comprises a pump-nozzle unit (2) having a compression space (4) for compressing fuel and an injector (5) for injecting compressed fuel into the respective cylinder, the compression space (4) being connected via a first Control valve (15) can be filled with fuel to be compressed and wherein the injector (5) connected to the compression chamber (4) nozzle chamber (6), one to the compression chamber (4) connected control chamber (8) via a second control valve (16 ) with the low-pressure side (18) is connectable, and a displaceable against the action of a closing force nozzle needle (11) which via a nozzle in the space (6), acting in the valve opening direction first control surface (12) and via a in the control chamber (8) located, acting in the valve closing direction second control surface (13) for closing and opening of injection openings (14) of the nozzle chamber (6) is actuated. DOLLAR A According to the invention, the first control valve (15) is designed as a slide valve with a valve slide (23) which is displaceable by an actuator (21) against the action of a first restoring force from a closed valve position to an open valve position, and that the second control valve ( 16) has a displaceable valve actuator (32), which by further advancing the valve spool (23) against the action of a second restoring force from an open valve position into a position of the valve ...

Description

The The invention is based on a fuel injection device the genus of claim 1.

Such a fuel injection device is, for example, by the DE 102 38 951 A1 known.

From DE 102 38 951 A1 known fuel injection device uses a so-called pump-nozzle unit (PDE injection system) for generating high injection pressures. The pump-nozzle unit comprises a pressure generating unit with a pump piston for pressure build-up, an injector for injecting the fuel into the combustion chamber of a cylinder and a control unit, for example an electromagnetic valve. Each engine cylinder has such a unit injector, which is located in the cylinder head and is operated for example via a rocker arm of an engine camshaft. The injector has a nozzle needle displaceable against the action of a closing spring, which has a first control surface located in a nozzle chamber and acting in the valve opening direction and a second control surface acting in a control chamber, acting in the valve closing direction, and closing or opening injection openings of the nozzle chamber. The filling of the pressure generating unit with fuel from a low-pressure system takes place during the upward movement of the pump piston. After the connection of the pressure generating unit to the low pressure system is shut off by a first control valve of the control unit, pressure is built up by the downward movement of the pump piston in the nozzle chamber and in the control chamber of the injector. The injection with the fuel located in the nozzle chamber into the combustion chamber of the cylinder takes place when the control chamber is connected to the low-pressure side via a second control valve of the control unit. As a result, the control chamber is depressurized, and the pressure prevailing in the nozzle chamber pressure is sufficient aufzusteuern the nozzle needle against the action of the closing spring.

at Although the known fuel device, the nozzle opening pressure be controlled flexibly throughout the map, however, must doing the operation the two control valves be timed exactly matched, which increased Tax expense required.

Advantages of invention

The Fuel injection device according to the invention with the characterizing features of claim 1 has the other hand Advantage that for both control valves a single actuator is provided and the two control valves in the direction of adjustment of the actuator with each other mechanically coupled. This ensures that the Valve spool is always in its open valve position, when the valve actuator of the second control valve is actuated.

Preferably the second restoring force is greater than the first restoring force, such that the valve actuator of the second control valve forms a stop, at the shifted from its closed valve position valve slide is applied.

Further Advantages and advantageous embodiments of the subject invention are the description, the drawings and the claims removable.

drawings

embodiments the fuel injection device according to the invention are shown in the drawings and in the following description explained in more detail.

It demonstrate:

1 a hydraulic circuit diagram of a first embodiment of the fuel injection device according to the invention;

2 a longitudinal section of in 1 schematically shown valve assembly;

3a to 3c enlarged detail views of slide and conical seat valves of the valve assembly according to III in 2 in different switching positions;

4 in the valve assembly of the 2 acting spring forces in response to the displacement of a valve spool of the slide valve; and

5 a hydraulic circuit diagram of a second embodiment of the fuel injection device according to the invention.

description the embodiments

In the 1 illustrated fuel injection device 1 for internal combustion engines comprises a pump-nozzle unit (PDE) 2 for each cylinder of the internal combustion engine. The pump-nozzle unit 2 has a pump piston 3 and a compression room 4 for compressing fuel as well as an injector 5 for injecting compressed fuel into the combustion chamber of the respective cylinder. The injector 5 has a nozzle space 6 that is via a supply line 7 to the compression room 4 connected, a control room 8th that has an inlet throttle 9 also to the compression room 4 connected, and one against the action of a closing spring 10 movable nozzle needle 11 on which one in the nozzle room 6 located, acting in the valve opening direction first control surface 12 and one in the control room 8th located, acting in the valve closing direction second control surface 13 for closing and opening injection openings 14 of the nozzle space 6 is operable. The control of the fuel injection via one of two-way control valves 15 . 16 formed valve assembly 17 , where the compression space 4 for filling with fuel via the first control valve 15 with a low pressure side (leakage line) 18 is connectable. About a relief line 19 with outlet throttle 20 is the control room 8th for pressure relief by means of the second control valve 16 with the low pressure side 18 connectable.

The two control valves 15 . 16 have a common actuator 21 and are mechanically coupled together such that the valve assembly 17 has a total of three different valve positions. The actuator 21 is a magnetic drive or a piezoelectric drive. In the in 1 shown first valve position is the first control valve 15 opened and the second control valve 16 closed, leaving the compression space 4 during the upward movement of the engine camshaft 22 actuated pump piston 3 is filled with fuel from the low pressure system. In the second valve position both control valves 15 . 16 closed, so by the downward movement of the pump piston 3 the pressure build-up in the nozzle chamber 6 and in the control room 8th he follows. The one in the control room 8th prevailing closing pressure and the closing force of the closing spring 10 are larger than the one in the nozzle chamber 6 prevailing opening pressure, so that the injection openings 14 remain closed. In the third valve position is the first control valve 15 closed and the second control valve 16 open. The control room 8th is relieved of pressure, and in the nozzle chamber 6 prevailing opening pressure is now sufficient, the nozzle needle 11 against the action of the closing spring 10 and in the control room 8th aufzusteuern prevailing Schließdrucks. As a result, in a simple, cost-effective manner, a flexible control of the opening pressure of the nozzle needle 11 in the range of 250 to 2000 bar possible.

In 2 is the valve assembly 17 shown in detail in their first valve position. The first control valve 15 is as a slide valve with a valve spool 23 is formed, in a bore of the valve housing 24 guided and by an actuator 25 of the actuator 21 against the action of a first return spring 26 in the direction 27 is displaceable. A valve sealing edge 28 on the valve spool 23 acts with a sealing edge 29 on the valve body 24 put together an annulus 30 into which the supply line 7 flows from an annulus 31 separates to which the leakage line 18 connected. In the in 2 shown first valve position are the two annular spaces 30 . 31 through the valve spool 23 not locked, ie, the supply line 7 and the leakage line 18 are connected. The second control valve 16 is as a cone seat valve with a valve actuator 32 formed in the guide bore of the valve body 24 coaxial with the valve spool 23 guided and against the action of a second return spring 33 in the direction 27 is displaceable. A conical valve sealing surface 34 on the valve actuator 32 acts with a conical valve seat surface 35 on the valve body 24 put together an annulus 36 in which the discharge line 19 flows from the annulus 31 separates. In the in 2 shown first valve position locks the valve actuator 32 the connection of the two annular spaces 31 . 36 ie, the discharge line 19 is not with the leakage line 18 connected.

The valve actuator 32 is axial between the valve spool 23 and the two return springs 26 . 33 arranged. The first return spring 26 is from the second return spring 33 Coaxially surrounds and acts on the valve spool 23 over a push rod 37 extending through an axial through bore of the valve actuator 32 extends.

In the in 3a shown first valve position is the valve spool 23 from the valve actuator 32 axially spaced by a distance d less than the maximum displacement D _max ( _FIG. 4 ) of the valve spool 23 through the actuator 21 is. In the in 3b shown second valve position is the valve spool 23 through the actuator 21 by the distance d = 0.25 mm against the action of the first return spring 26 moved so that the valve slide 23 on the valve actuator 32 is applied. By further advancing the valve spool 23 by a total of D _max = 0.4 mm by the actuator 21 becomes the valve actuator 32 from the valve spool 23 in the direction 27 taken along, taking on the valve spool 23 and the valve actuator 32 now both return springs 26 . 33 Act. As 3c clearly shows is between valve body 24 and front end of the valve spool 23 an annular gap 38 provided see, in the third valve position, the two annular spaces 31 . 36 connected to each other.

This in 4 Diagram shown points to the valve spool 23 acting spring force F as a function of the displacement x of the valve spool 23 , Up to a displacement x <d acts on the valve spool 23 with the displacement x steadily increasing spring force of the return spring 26 , As soon as the valve spool 23 on the valve actuator 32 comes to rest, ie at x = d occurs, since now both return springs 26 . 33 on the valve spool 23 act, a jump-like Federkrafterhöhung by more than double. The spring force then increases steadily with the further displacement path until the maximum displacement D _{max is} reached. Due to the sudden spring force increase, the valve actuator forms 32 a stop for the shifted in its open valve position valve spool 23 ,

From the fuel injector 1 is different in the 5 shown fuel injector 1' through the training of the injector 50 as a so-called coaxial vario-nozzle (KVD). In 5 are functionally identical parts with the same reference numerals as in 1 designated. The injector 50 one has the nozzle needle 11 Coaxially surrounding hollow outer nozzle needle 51 on, against the action of a closing spring 52 displaceable and one in the nozzle chamber 6 located, acting in the valve opening direction control surface 53 for opening second injection openings 54 of the nozzle space 6 is operable. When in the nozzle room 6 prevailing opening pressure greater than the closing force of the closing spring 52 is, the outer valve needle 51 controlled, and the fuel injection takes place via the second injection openings 54 , By relieving the control room 8th then also the inner valve needle 11 piloted so that the fuel injection over both injection ports 14 . 54 he follows. About the control room 8th , only on the inner nozzle needle 11 acts, thus the above-mentioned advantages are available. In particular, the inner nozzle needle can be 11 in the range of approx. 300 bar up to max. Pressure, ie approx. 2000 bar, flexible by the control current of the actuator (eg solenoid valve) 21 actuate. This allows the opening behavior of the inner nozzle needle 11 controlled and the so-called jump in quantity in the map are avoided. Depending on the application and the motor requirements, it is also possible to respond quickly and flexibly and to achieve a smooth adaptation to specific motor requirements.

Claims (9)

Fuel injection device ( 1 ; 1' ) of an internal combustion engine, each with a provided for each cylinder of the internal combustion engine pump-nozzle unit ( 2 ) with a compression space ( 4 ) for compressing fuel and an injector ( 5 ; 50 ) for injecting compressed fuel into the respective cylinder, the compression space ( 4 ) via a first control valve ( 15 ) is fillable with fuel to be compressed and wherein the injector ( 5 ; 50 ) one to the compression space ( 4 ) connected nozzle space ( 6 ), one to the compression space ( 4 ) connected control room ( 8th ), which via a second control valve ( 16 ) with the low pressure side ( 18 ) is connectable, and a displaceable against the action of a closing force nozzle needle ( 11 ), which via a in the nozzle chamber ( 6 ), acting in the valve opening direction first control surface ( 12 ) and one in the control room ( 8th ) acting in the valve closing direction second control surface ( 13 ) for closing and opening injection openings ( 14 ) of the nozzle space ( 6 ) is actuated, characterized in that the first control valve ( 15 ) as a slide valve with a valve slide ( 23 ) is formed by an actuator ( 21 ) is displaceable against the action of a first restoring force from a closed valve position into an open valve position, and that the second control valve ( 16 ) a displaceable valve actuator ( 32 ), which by further advancing the valve spool ( 23 ) is taken against the action of a second restoring force from an open valve position to a closed valve position. Fuel injection device according to claim 1, characterized in that the valve spool ( 23 ) in its closed valve position by the valve actuator ( 32 ) is axially spaced by a distance (d) which is less than the maximum displacement (D _max ) of the valve spool ( 23 ) by the actuator ( 21 ). Fuel injection device according to claim 1 or 2, characterized in that the second control valve ( 16 ) is designed as a seat valve, in particular as a conical seat valve. Fuel injection device according to one of the preceding claims, characterized in that the actuator ( 21 ) is a magnetic drive or a piezoelectric drive. Fuel injection device according to one of the preceding claims, characterized in that the valve slide ( 23 ) and the valve actuator ( 32 ) are arranged coaxially with each other and in particular axially one behind the other. Fuel injection device according to one of the preceding Claims, characterized in that the second restoring force is greater than the first restoring force, preferably at least twice as large. Fuel injection device according to one of the preceding claims, characterized in that the first restoring force by a on the valve spool ( 23 ) acting return spring ( 26 ) and the second restoring force by the first return spring ( 26 ) and one on the valve actuator ( 32 ) of the second control valve ( 16 ) acting second return spring ( 33 ) is formed. Fuel injection device according to claim 7, characterized in that the first return spring ( 26 ) coaxially with the second return spring ( 33 ) is surrounded and on the valve spool ( 23 ) via a push rod ( 37 ), which extends through an axial through hole of the valve actuator ( 32 ). Fuel injection device according to one of the preceding claims, characterized in that the injector ( 50 ) one the nozzle needle ( 11 coaxially surrounding hollow outer nozzle needle ( 51 ) which is displaceable against the action of a closing force and via a in the nozzle chamber ( 6 ), acting in the valve opening direction control surface ( 53 ) for opening injection openings ( 54 ) of the nozzle space ( 6 ) is operable.