DE102004002088A1 - Pressure-controlled CR injector for fuel injection into combustion chambers of internal combustion engines, in particular diesel engines - Google Patents

Abstract

A pressure-controlled common-rail injector for fuel injection into combustion chambers of internal combustion engines, in particular diesel engines, has a 3/2-way valve (15, 16, 22, 23, 26, 27) accommodated in a valve body (11, 11a). on, which for controlling a in a nozzle body (13) arranged axially movable, a nozzle outlet (41, 41 a, 41 b) actuating nozzle needle (32, 32 a, 32 b) is used. The 3/2-way valve has a high-pressure actuated servo piston (15, 16) which cooperates with a sealing seat (23) of the valve body controlling the fuel supply to the nozzle outlet (41, 41a, 41b). DOLLAR A essential feature is that the sealing surface (22) of the servo piston (15, 16) of the 3/2-way valve and the sealing seat (23) in the valve body (11, 11 a) is formed in each case as a flat seat.

Description

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The This invention relates to a pressure controlled CR injector the preamble of claim 1.

pressure-controlled Common rail injectors are distinguished over stroke-controlled systems as a result from that they have high specific benefits while reducing allow pollutant emissions. Leave it a - preferred - nozzle needle movement with fast needle speeds and - by pressure wave effects - an increase of the Injection pressure over reach the rail pressure.

The control of a pressure-controlled CR injector is usually carried out by a so-called. 3/2-way valve. To be able to control the flows of the necessary large amounts of fuel exactly, servo valves are preferably used in conical seat slide design. Such known servo valves, such as the EP 011766306 A2 shows are designed with one-piece servo needle and one-piece servo piston. As a result, many dependent tolerance dimensions are conditional, which has difficulties and high costs in the production result. In addition, no adjustability is possible. In addition, the sealing seat of the known servo valves is exposed to a high load, which can lead to deformations in the seating area.

task the invention is to provide a pressure controlled CR injector, who are without big Can make effort and the easy adjustability of acting on the sealing seat hydraulic closing forces allows.

Advantages of invention

According to the invention Task with an injector of the type described by the characterizing Characteristics of claim 1 solved.

advantageous Embodiments of the basic idea of the invention contain the claims 2 to 10th

Basically it is possible the flat seat according to the invention as exact circular To perform sealing edge. In this case, the servo piston needs only a comparatively small hydraulic closing force to be charged. To simplify the seat sanding process However, a simple flat ground seat in conjunction with a then required, correspondingly large hydraulic closing force advantageous. The required, acting on the sealing seat hydraulic closing force can be without difficulty on the area difference from opening and closing pressure surface arbitrarily to adjust.

If the sealing seat is designed as a flat seat, the special results Advantage that as a valve body a multi-part housing can be used, since it is then possible, always occurring Offset the components offset in a simple manner. These constructive conception possible a simple and inexpensive Manufacturability of the injector according to the invention.

drawing

to Illustrative of the invention are exemplary embodiments, which in the Drawing shown and described in detail below. It shows (in each case schematically and in vertical longitudinal section):

1 an embodiment of a pressure-controlled CR injector with a one-piece valve body,

2 another embodiment of a pressure-controlled CR injector, in which the valve body is formed in two parts,

3 a further embodiment of a pressure-controlled CR injector, in which a pressure booster is interposed between the 3/2-way valve and the nozzle body,

4 a further variant of a pressure-controlled CR injector, in which a so-called. Vario nozzle is used to increase the flexibility of the injection.

description the embodiments

In 1 designated 10 a - as a dashed line highly schematically indicated - injector, the - including - a valve body 11 and one in the flow direction 12 downstream nozzle body 13 receives. In a stepped axial recess 14 is a total with 15 numbered servo piston arranged axially displaceable, the - in the lower section - a valve piston 16 forms. servo piston 15 and valve piston 16 are of a continuous centric throttle bore 17 interspersed. Below the valve piston 16 is a housing part 18 with an enlarged bore 19 arranged, to which a further housing part 20 With a hole 21 connects, but whose diameter is much smaller than the diameter of the (enlarged) bore 19 , The hole 21 is via a high pressure line 24 with a pressure accumulator 25 (so-called common rail) hydraulically connected.

At its lower end face 22 forms the valve piston 16 a planar sealing surface with a sealing seat 23 on the top of the housing part 20 interacts. The seal seat 23 is - as well as the mating surface 22 on the valve piston 16 - Planar trained, so represents a flat seat.

The valve piston 16 also has the function of a slider. He acts here with its cylindrical peripheral surface into which a recess 26 is incorporated, with one at the top of the housing part 18 trained slide sealing edge 27 hydraulically together. In the in 1 illustrated closed position of the valve piston 16 - flat seat 23 and level counterface 22 are here in sealing contact - connects the valve piston 16 in its slide function, the bore 19 with one below the servo piston 15 located pressure chamber 28 caused by a cross-sectional widening of the axial recess 14 is formed. Above the servo piston 15 forms the axial recess 14 a servo control room 29 , pressure chamber 28 and servo control room 29 are not hydraulically connected because of the servo piston 15 in the valve body 11 or in the axial recess 14 pressure-tight is performed. The pressure room 28 is however through a return line 30 connected to the low pressure part (not shown) of the system.

One from the hole 19 outgoing high pressure line 31 leads into the nozzle body 13 and there in a a nozzle needle 32 surrounding nozzle space 33 , The nozzle needle 32 is with a thickened middle section 34 in a hole 35 of the nozzle body 13 guided and at its upper end by a compression spring 36 applied. The compression spring 36 sits on a tapered pin part 37 the nozzle needle 32 and is in a room 38 housed, via a return line 39 is connected to the (not shown) low pressure part of the system.

At its lower end forms the nozzle needle 32 a closing body 40 , with one in the nozzle body 13 trained nozzle exit 41 interacts. From the nozzle outlet 41 the fuel enters the associated combustion chamber of the relevant internal combustion engine.

Above the valve body 11 joins in 42 numbered further housing part, in which a solenoid control valve 43 is housed. In the out 1 apparent closing position of the solenoid control valve 43 will - from a valve room 45 out - about a throttle 44 the servo control room 29 driven. In opening position of the solenoid control valve 43 however, it gets into the valve chamber 45 located fuel via a return line 46 in the low pressure part of the system.

Of the in the above described in its structural design injector works like this.

At rest, the sealing seat 23 through the servo or valve piston 15 respectively. 16 closed. As a result, there are nozzle space 33 and supply line 31 depressurized and via the slide valve 26 . 27 with the return 30 (Low pressure system) connected. The nozzle needle 32 is closed, and there is no injection.

To the valve 16 . 23 To open, first the solenoid control valve 43 activated (opened) and thereby the servo control room 29 depressurized. The one with the valve piston 16 a common component forming servo piston 15 moves as a result of the bore 21 out on the valve piston surface 22 acting pressure force upward, thereby opens the sealing edge 23 and closes the sealing edge 27 , Through the throttles 17 and 44 can be the speed of movement of the servo piston 15 set as desired. The high pressure (rail pressure) in the bore 21 constantly brings a defined opening force on the valve piston 16 and thus on the servo piston 15 , This results in an exact valve movement and a stable persistence at the opening stop in the open state.

With servo and valve piston open 15 . 16 becomes the nozzle space 33 the injection nozzle (nozzle outlet 41 ) disconnected from the return and now on the supply line 31 supplied with fuel under high pressure (rail pressure). The nozzle exit 21 opens, and the injection begins.

To stop the injection process, first the solenoid control valve 43 be closed again (by de-energizing it) (see position in 1 ). In the servo control room 29 System pressure builds up, and the pressure force moves servo and valve pistons 15 . 16 down to its initial position (closed position, s. 1 ). At the same time the valve becomes 22 . 23 closed and the slide valve 26 . 27 open.

Because the closing pressure surface in the room 29 is greater than the opening pressure area in the hole 21 , is an accurate and fast closing movement of the servo and valve piston 15 . 16 reached. To support the valve movement can also be in addition - from the room 29 forth the servo piston 15 acted upon - spring (compression spring) pre will see. However, there are no springs necessary for functional representation, resulting in a very compact design of the servo valve 15 . 16 . 22 . 23 . 29 makes possible.

By closing the servo and valve piston 15 . 16 be nozzle room 33 and supply line 31 depressurized and connected to the return (low pressure system). The nozzle needle 32 closes and the injection is over.

The variant of the injector 2 is similar to most embodiment details of the embodiment 1 , so in 2 largely the same reference numerals as in 1 Could be used. The same applies with regard to the mode of operation. A related (re) function description of the variant 2 is therefore unnecessary.

A (constructive) feature of the embodiment according to 2 is, however, that of the servo and valve piston 15 . 16 receiving valve body is formed in two parts. It is a servo and valve piston 15 . 16 immediately receiving inner valve body part 11a and a cup-shaped outer valve body part enclosing this 11b , Between the outer wall of the inner

Valve body part 11a and the inner wall of the outer valve body part 11b extends a ring-cylindrical space 47 , which at its upper end by an annular sealing element 48 is closed. The annular cylindrical space 47 is through the pressure line 24 to the accumulator 25 (Common rail) connected. About one in the housing part 20 incorporated radial channel 49 is the hole 21 with the annular cylindrical space 47 in hydraulic connection, so that there prevail as here, the same pressure conditions.

In the embodiment according to 2 So is the inner valve body part 11a as a "cartridge" running radially from the outside - through the annular cylindrical space 47 located, under high pressure liquid - is at least partially pressurized with system pressure. This can cause a widening of the needle guides of the servo and valve piston 15 . 16 be counteracted, and the material stresses occurring, z. B. bore intersections, can be reduced thereby.

The according to the variant 2 applied constructional measure of a two-part valve body 11a . 11b is due to the planar design of sealing seat 23 (on the housing part 20 ) and mating surface 22 (on the valve piston 16 ) favors or allows. Because of such a flat seat valve seal, it is possible, one between the two valve body parts 11a and 11b compensate for any axis misalignment.

Due to the closing pressure force in the servo control room 29 By the way, enough closing force is available to the flat seat 23 To guarantee a high surface pressure and thus a good tightness.

The variant after 3 largely corresponds to the embodiment according to 1 so that the same reference numerals could be used to that extent. A special feature of the embodiment according to 3 lies in the fact that the 3/2-way valve 15 . 16 . 22 . 23 . 26 . 27 to increase the injection pressure, a pressure booster 50 is downstream. The pressure intensifier 50 is in the supply line 31 , which - from the valve space (extended bore 19 ) come the nozzle space 33 supplied with high-pressure fuel, interposed. It is one of two piston sections 51 . 52 different diameter existing translating piston, in a room 53 a translator housing 54 is housed. Both sides (top and bottom) of the booster piston 51 . 52 are in the translator housing 54 two pressure chambers 56 . 57 formed of different cross-section. The supply line 31 first flows into the pressure chamber 56 , This is through a in the translator housing 54 built-in throttle bore 55 with the (lower) pressure chamber 57 hydraulically connected. In the throttle hole 55 is a check valve 58 arranged. From the pressure chamber 57 then finally takes it into the nozzle chamber 33 opening lower section of the supply line 31 his exit. The operation of such a pressure booster is known, so that in this respect detailed explanations are unnecessary.

Also in the variant 4 as far as they are according to the embodiment 1 corresponds, the same reference numerals as used there. The peculiarity of the embodiment according to 4 is that as a nozzle outlet a Variodüse 41a . 41b serves, which cooperates with two concentrically arranged nozzle needles. This is an inner nozzle needle 32a from a compression spring 36a and an outer nozzle needle 32b from a compression spring 36b applied. The compression springs 36a and 36b are - concentric with each other - in a common space 38 of the nozzle housing 13 arranged. The control of the two nozzle needles 32a and 32b can either over the compressive forces of the springs 36a . 36b or additional measures may be taken to actively control the internal nozzle needle 32a be provided.

Claims (10)

Pressure-controlled common-rail injector for Fuel injection into combustion chambers of internal combustion engines, in particular diesel engines, with a in a valve body ( 11 . 11a ) 3/2-way valve ( 15 . 16 . 22 . 23 . 26 . 27 ), which is used to control one in a nozzle body ( 13 ) arranged axially movable, a nozzle outlet ( 41 . 41a . 41b ) actuating nozzle needle ( 32 . 32a . 32b ), wherein the 3/2-way valve is a high pressure actuated servo piston ( 15 . 16 ), which with one the fuel supply to the nozzle outlet ( 41 . 41a . 41b ) controlling sealing seat ( 23 ) of the valve body, characterized in that the sealing surface ( 22 ) of the servo piston ( 15 . 16 ) of the 3/2-way valve and the sealing seat ( 23 ) in the valve body ( 11 . 11a ) is formed in each case as a flat seat. Injector according to claim 1, characterized in that the sealing surface ( 22 ) of the servo piston ( 15 . 16 ) and sealing seat ( 23 ) in the valve body ( 11 . 11a ) are each formed planar. Injector according to claim 1, characterized in that the servo piston ( 15 . 16 ) a flat sealing surface ( 22 ) and the flat seat in the valve body is designed as a circumferential sealing edge. Injector according to claim 1, characterized in that the servo piston as a flat seat has a peripheral sealing edge and the flat seat ( 23 ) in the valve body ( 11 . 11a ) is designed as a flat sealing surface. Injector according to one or more of the preceding claims, characterized in that the servo piston ( 15 . 16 ) receiving valve body ( 11 . 11a ) is formed in several parts ( 2 ). Injector according to claim 5, characterized in that a servo piston ( 15 . 16 ) immediately receiving inner valve body ( 11a ) in a cup-shaped outer valve body ( 11b ) is arranged. Injector according to claim 6, characterized in that a the inner valve body ( 11a ) receiving recess of the outer valve body ( 11b ) has a larger diameter than the inner valve body ( 11a ), such that between the outer wall of the inner valve body ( 11a ) and the inner wall of the outer valve body ( 11b ) a ring-cylindrical space ( 47 ). Injector according to claim 7, characterized in that the sealed to the outside ( 48 ) annular cylindrical space ( 47 ) high pressure ( 24 . 25 ). Injector according to one or more of the preceding claims, characterized in that the 3/2-way valve ( 15 . 16 . 22 . 23 . 26 27 ) to increase the injection pressure, a pressure booster ( 50 ) is downstream ( 3 ). Injector according to one or more of the preceding claims, characterized in that a Vario nozzle ( 41a . 41b ), which with two concentrically arranged nozzle needles ( 32a respectively. 32b ) cooperates ( 4 ).