EP2102486B1 - Injector with an axial pressure-compensating control valve - Google Patents

Abstract

The injector (1) has a control valve (24) with a valve piston (26) adjusted by an actuator (40) e.g. electromagnetic drive. The piston is arranged in a valve chamber (23) connected with a control chamber (15), where low pressure is formed on piston's front sides. The piston is guided in a casing (27) in the valve chamber. A spring (29) in the valve chamber has ends respectively supported at the casing and the piston. The spring presses the piston on a valve seat (32) and the casing on a base surface (33), where piston diameter within the casing corresponds to piston diameter at the seat.

Description

State of the art

The invention relates to an injector according to the preamble of claim 1.

The DE 103 53 169 A1 describes a common rail injector with a control valve for blocking and opening a fuel drain path from a control chamber. For actuating the control valve, a piezoelectric actuator is provided, which acts via a translation piston in the axial direction on a valve piston adjusting. By means of the designed as a 3/2-way valve control valve, the fuel pressure can be influenced within a control chamber, the control chamber is supplied via a pressure channel with inlet throttle and an additional channel with fuel from a high-pressure fuel storage. By varying the fuel pressure within the control chamber, a nozzle needle is moved between an open position and a closed position, wherein the nozzle needle in its open position releases the fuel flow into the combustion chamber of an internal combustion engine. Since the known control valve is not pressure balanced in the axial direction, high actuating forces for opening the control valve are required.

From the EP 1 612 403 A1 is a common rail injector with a pressure balanced in the axial direction control valve known. The known control valve has as an adjustable valve element on an axially displaceable sleeve, which only is acted upon in the radial direction with fuel pressure from a high pressure area. Due to the use of a pressure balanced control valve only small actuating forces for opening the control valve are required, so that the setting task is performed in the known injector of an electromagnetic drive. Would you do that from the EP 1 612 403 A1 known control valve on the from the DE 103 53 169 A1 transfer the known injector, the overall configuration of the injector would have to be changed. In particular, the low-pressure chamber would have to be laid much further in the direction of the control chamber in the piezo-actuated injector.

Disclosure of the invention Technically task

The invention is therefore based on the object to propose an injector with an alternatively designed axially-pressure balanced valve, which is particularly suitable for the use of an electromagnetic actuator.

Technical solution

This object is achieved with the features of claim 1; the dependent claims indicate more favorable developments. In addition, all combinations of at least two features disclosed in the description, the drawing and / or the claims fall within the scope of the invention.

The invention is based on the idea, instead of an axially adjustable sleeve an adjustable in the axial direction Provide valve piston for opening and closing the control valve. The valve piston (bolt) is disposed within a valve chamber which is hydraulically connected to the control chamber, so that when the control valve is open fuel through a fuel drain path from the control chamber via the valve chamber can flow to a low-pressure chamber. When the control valve is closed, the fuel drain path is blocked. The valve piston is not guided according to the invention directly in a throttle plate, but in a sleeve which is received in the valve chamber. In order to bias the valve piston in the closing direction on a valve seat and simultaneously prevent lifting of the sleeve from a bottom surface (sealing surface) of the valve chamber, a spring is provided, on the one hand on the valve piston, in particular on the underside of a valve head and on the other hand on the sleeve, in particular on the end face of the sleeve, supported. So that on the valve piston in the axial direction no or only minimal pressure forces act, so it is a pressure balanced in the axial direction control valve, it is provided that low pressure is applied to both end faces of the valve piston and that in the axial direction acted upon by low pressure (projection) Areas of the valve piston are equal on both sides. Since the valve seat facing the end face of the valve piston limits the low-pressure chamber or is directly connected hydraulically with this, is automatically low pressure on the end face. The application of this (upper) end face opposite (lower) end face with low pressure can be realized, for example, that at the end facing away from the valve seat end of the valve piston, a connecting channel is performed, the immediately adjacent to this end face area hydraulically connected to the low pressure area of the injector. Depending on the operating state, in the low-pressure region, in particular in the low-pressure space, of the injector, fuel pressures in a range between approximately 0 and 10 bar prevail, whereas the fuel flowing from a high-pressure fuel reservoir into the injector is under a pressure in a range between approximately 1800 and 2000 bar. The inventive design of the injector can be easily to the from DE 103 53 169 A1 transferred in this case, preferably in place of an additional fuel supply to the valve chamber, a low-pressure connection line can be provided to supply the nozzle needle facing the end face of the valve body with low pressure. In particular, but not necessarily, instead of a piezo actuator, an electromagnetic drive can be used.

In a further development of the invention is advantageously provided that the sleeve is received with radial play in the valve chamber, so that pressurized fuel in the valve chamber exerts a radially inwardly acting force on the sleeve, so that a widening of the guide clearance between the sleeve and the valve piston avoided during operation and thus leakage losses are minimized.

In an embodiment of the invention is advantageously provided that the hydraulic connection between the control chamber and the valve chamber is realized via a drain passage with outlet throttle, wherein the cross sections of the outlet throttle and in which the control chamber supplying pressure channel arranged inlet throttle are coordinated such that when the control valve is open net fuel outflow results in the low pressure space. Preferably, the drainage channel opens into the valve chamber in a region between the sleeve and the valve chamber inner wall. This makes it possible to integrate the flow channel exclusively in a arranged between the control chamber and the valve chamber throttle plate.

As already mentioned, the injector is particularly suitable for the use of a solenoid actuator, since due to the axial pressure balance of the control valve comparatively low actuating forces must be applied. The electromagnetic drive has at least one electromagnet (coil) and at least one armature plate interacting therewith, the armature plate having to be operatively connected to the valve piston. Since in an electromagnetic drive no minimum pressure for acting on a translation piston of a piezo actuator must be present, the low pressure level can be lower, whereby the return system for the fuel can be designed more cost-effective overall.

In particular, the anchor plate is operatively connected to a push rod, for example, integrally formed therewith, wherein the armature plate facing away from the free end of the push rod on the valve piston, in particular the valve piston head, is centered. As a result, the adjusting force of the electromagnetic drive via the armature plate and are transmitted from the latter via the push rod on the valve piston to lift it from the valve seat and thus release the fuel discharge path to the low pressure space, which in turn lifts the nozzle needle from its needle seat and the fuel flow in one Combustion chamber releases.

The stroke of the electromagnetic drive can be adjusted via the variation of the length of the push rod.

To realize the centering of the push rod on the end face of the valve piston a concave-convex pairing between valve piston and push rod is advantageously realized, wherein preferably the push rod in the region of its free end convex and the end face of the valve piston is designed concave accordingly.

In order to ensure contact of the armature plate, the push rod and the valve piston even when not energized solenoid drive, a weak biasing spring is preferably provided, which biases the armature plate and thus the push rod in the direction of the valve piston. However, the spring force must be such that it is less than the spring force of the spring within the valve chamber, which presses the valve piston in the opposite direction in its valve seat.

In order to ensure sufficient coaxiality during the adjustment, the invention is provided in a further development that the push rod is guided within a stop sleeve, wherein the stop sleeve is received within the electromagnet of the solenoid drive and has a stop surface for the anchor plate.

In an embodiment of the invention is advantageously provided that the valve chamber is limited on its side facing the control chamber of a throttle plate, the throttle plate thus forms the bottom surface of the valve chamber on which the guide sleeve is supported within the valve chamber. In this throttle plate is advantageously introduced and the drainage channel with outlet throttle from the control chamber.

In addition, there is advantageously within the throttle plate, a connecting channel which connects the nozzle needle facing the end face of the valve piston with the low pressure region of the injector, so preferably at least approximately the same (low) pressure prevails on both end faces of the valve piston.

Brief description of the drawings

Fig. 1:

eine geschnittene Teilansicht eines Injektors mit in axialer Richtung druckausgeglichenem Steuerventil,

Fig. 2:

eine Detailansicht eines Injektors, aus der die hydraulische Verbindung zwischen Steuer- kammer und Ventilkammer ersichtlich ist,

Fig. 3:

eine vergrößerte Detailansicht der Einbausituation einer Ankerplatte eines Elekt- romagnetantriebes des Injektors, und

Fig. 4:

eine einstückige Baueinheit aus Ankerplatte und Druckstange.

Further advantages, features and details of the invention will become apparent from the following description of preferred embodiments and from the drawing; this shows in:

Fig. 1:

3 a sectional partial view of an injector with a pressure-balanced control valve in the axial direction,

Fig. 2:

a detailed view of an injector showing the hydraulic connection between the control chamber and the valve chamber,

3:

an enlarged detail of the installation situation of an anchor plate of an Ele- romagnetantriebes of the injector, and

4:

a one-piece assembly of anchor plate and push rod.

Embodiments of the invention

In the figures, the same components and components with the same function with the same reference numerals.

In the Fig. 1 and 2 a common rail injector 1 is shown. The injector 1 has an injector body 2, a nozzle body 3 shown only in sections, and a valve body 4 lying against the injector body 2 and a throttle plate 5 arranged between the valve body 4 and the nozzle body 3. A screwed with the injector 2 nozzle retaining nut 6, which is penetrated in the axial direction of the nozzle body 3, generates an axial biasing force, which clamps the nozzle body 3, the throttle plate 5, the valve body 4 and the injector body 2 against each other.

Within the nozzle body 3, a guide bore 7 is formed, in which an elongated nozzle needle 8 is guided axially movable. At a needle point 9, the nozzle needle has a closing surface 10 with which it can be brought into tight contact with a needle seat 11 formed inside the nozzle body 3.

When the nozzle needle 8 abuts the needle seat 11, ie, is in a closed position, the fuel outlet from a nozzle hole arrangement 12 is blocked. If, on the other hand, it is lifted by the needle seat 11, fuel can flow from a pressure chamber 13 in the axial direction along the nozzle needle 8 past the needle seat 11 to the nozzle hole arrangement 12 and be sprayed there substantially under high pressure (rail pressure) into a combustion chamber.

The nozzle needle 8 is biased by means of a biasing spring, not shown, in the direction of its closed position.

The upper end face 14 of the nozzle needle 8 protrudes into a control chamber 15, which is bounded on the opposite side of the end face 14 of the throttle plate 14. The control chamber 15 is supplied via a pressure channel 16 with inlet throttle 17 and a connection pocket 20 in the valve body 4 with fuel under high pressure from a supply line 18, wherein the supply line 18 is connected to a fuel high-pressure accumulator, not shown, which is pressurized, for example via a radial piston pump , The supply channel 18 is simultaneously connected via a connecting bore 19 within the throttle plate 5 with the control chamber 15 radially enclosing the pressure chamber 13. About one Fig. 2 apparent flow channel 21 with outlet throttle 22 within the throttle plate 5, the control chamber 15 is hydraulically connected to a valve chamber 23 of a control valve 24 within the valve body 4. The drainage channel 21 is part of a fuel drainage path from the control chamber to a arranged in the plane above the valve chamber 23 low-pressure space 25. From there, the fuel can flow through a return line, not shown.

As mentioned, a closing force is exerted on the nozzle needle 8 by a biasing spring, not shown, at the same time is exercised by the pressure prevailing in the control chamber 15 fuel pressure on the end face 14 of the nozzle needle 8, a closing force on this. These closing forces act on the basis of the action of fuel pressure on a formed on the nozzle needle 8, not shown, step surface resulting opening force. The control valve 24 is in a closed position and the fuel drain from the control chamber 15 is locked in the low pressure chamber 25, the stationary force acting on the nozzle needle 8 closing force is greater than the opening force, which is why the nozzle needle 8 then assumes its closed position. When the control valve 24 is then opened, fuel flows out of the control chamber and the nozzle needle 8 is lifted from its needle seat 11.

The flow cross sections of the inlet throttle 17 and the outlet throttle 21 are matched to one another such that the inflow through the pressure channel 16 is weaker than the outflow through the outlet channel 21 and thus results in a net outflow of fuel when the control valve 24 is open. The resulting pressure drop in the control chamber 15 causes the amount of the closing force falls below the amount of the opening force and the nozzle needle 8 lifts off the needle seat 11.

Within the valve chamber 23, an axially displaceable valve piston 26 is arranged, which is guided in a sleeve 27 with the least possible backlash. The sleeve 27 is received with radial clearance within the valve chamber 23. Axially between the sleeve 27 and a valve piston head 28, a helical spring 29 is arranged, which is supported on the one hand on an upper end face 30 of the sleeve 27 and on the other hand on a lower annular shoulder 31 of the valve piston head 28 and so the valve piston 26 in the plane of the drawing in the direction of low pressure space 25 on biases a valve seat 32. At the same time, the sleeve 27 is sealingly pressed on a bottom surface 33 of the valve chamber 23, the bottom surface 33 being formed by a surface of the throttle plate 5. The cross-sectional area of the valve piston 26 sealed at the valve seat 32 corresponds to the cross-sectional area of the valve piston 26 guided inside the sleeve 27. In other words, the diameter of the valve seat 32 corresponds to the inner diameter of the sleeve 27. With its upper end face 34 in the plane of the drawing, the valve piston 26 projects into the area of the low pressure space 25 inside. Via a connecting channel 35 within the throttle plate 5, the space 36 is connected in the drawing plane below the valve piston 26 to the low pressure region of the injector 1. In particular, a not shown, vertical bore within the throttle plate 5 and the valve body 4 leads to the low-pressure chamber 25 or directly to a return line, not shown, to which also the low-pressure chamber 25 is connected. Thus, the same (low) pressure prevails on both end faces of the valve piston 26. Due to the at least approximate identity of the acted upon by low pressure surfaces of the valve piston, the valve piston is pressure balanced in the axial direction.

How out Fig. 2 can be seen, the drain passage 21 from the control chamber 25 opens into a pocket 37 in the valve body 4. The pocket 37 is connected to an annular space 38 between sleeve 27 and valve chamber wall 39, so that fuel from the control chamber 15 can flow into the valve chamber 23. The annular space 38 ensures that the guide clearance between valve piston 26 and sleeve 27 does not expand, so that leakage losses are minimized. At the same time, the fuel pressure within the valve chamber 23 ensures in that, in addition to the axial spring force of the helical spring 29, an axial force acts on the sleeve 27 in the direction of the throttle plate 5, so that the sleeve 27 sealingly bears against the bottom surface 33. Any leakage losses are removed via the connecting line 35.

In the drawing plane upper part of the valve body 4, an electromagnetic actuator 40 is arranged with an electromagnet 41. The electromagnet 41 is received in a bore 42, which guides the electromagnet 41 over its inner diameter. The electromagnet 41 is biased by a spring element 43 axially against the lower side in the drawing plane of the injector body 2. Within the injector body 2, a stepped bore 44 is provided, the axis of symmetry of which corresponds to the axis of symmetry of the valve piston 26. A first shoulder 45 of the stepped bore 44 limits the axial mobility of an armature plate 46, which cooperates with the electromagnet 41. Centrally supported on the armature plate 46 and in a receiving bore of the armature plate 46 is a push rod 47 which transmits a movement of the armature plate 45 to the valve piston 26 and thus controls the movement of the valve piston 26. The push rod 47 is centered with its convex free end 48 on the concave end face 34 of the valve piston 26. The push rod 47 is guided in a stop sleeve 49 near the anchor plate 46, wherein the stop sleeve 49 is received in a central passage opening of the electromagnet 41. The stop sleeve 49 has on its upper end face a stop surface 50 for abutment of the armature plate 46 upon energization of the electromagnet 41. The armature plate 46 is pressed via a weak biasing spring 51, which is supported on the valve body 2, via the push rod 47 against the valve piston 26, so that these parts are in contact. The contacting of the electromagnet 41 is guided via a housing part 52 in the upper plane in the drawing injector body to be able to lead the contact with the plug, not shown on the injector head, not shown.

When current is applied to the electromagnet 41, a tensile force acts between the armature plate 46 and the electromagnet 41, which is greater than the difference between the spring forces of the springs 29 and 51. As a result, the armature plate 46 moves downwards in the plane of the drawing until it stops against the abutment surface 50 of the stop sleeve 49 In this case, the control valve 24 is opened by lifting the valve piston 26 from the valve seat 32, so that the fuel drain path from the control chamber 15 is released to the pressure chamber 25.

In Fig. 3 the installation situation of the anchor plate 46 is shown. The armature plate 46 is received between the injector body 2 and the valve body 4. The distance a between the valve body 4 and the underside of the armature plate 46 is the armature stroke when the electromagnet 41 is energized. The distance b between the upper side of the armature plate 46 and the injector body 2 is the so-called overtravel. Since the push rod 47 and the anchor plate 46 at the closing time still have kinetic energy, they are moved in the direction of flight F until the anchor plate 46 abuts against the first shoulder 45 of the stepped bore 44. This additional route is referred to as overrunning b and should be designed as low as possible to spend the control valve as soon as possible after an operation in a state of rest.

Fig. 4 shows a one-piece design between anchor plate 46 and push rod 47. In this case, the armature stroke can be adjusted by a targeted grinding in the length of the push rod 47.

Claims (10)

1. Injector for injecting fuel into combustion chambers of an internal combustion engines, in particular common rail injector, having a control valve (24) which comprises a valve piston (26) which can be moved in the axial direction by means of an actuator (40) as a result of which a fuel discharge path which leads from a control chamber (15) to a low pressure space (25) can be opened or closed, wherein, by opening and closing the fuel discharge path the pressure in the control chamber (15), which can be supplied with fuel via a pressure duct (16) can be influenced, as a result of which a nozzle needle (8) which is operatively connected to the control chamber (15) can be moved between an open position, which enables a fuel flow, and a closed position
   characterized
   in that the valve piston (26), on whose two front sides low pressure is present, is arranged in a valve chamber (23) which is hydraulically connected to the control chamber (15), and said valve piston (26) is guided within a sleeve (27) which is held in the valve chamber (23), and in that a spring (29), which is supported at one end on the sleeve (27) and at the other end on the valve piston (26), is provided in the valve chamber (23), said spring (29) pressing the valve piston (26) onto a valve seat (32) and the sleeve (27) onto a bottom face (33) lying opposite, and in that the diameter of the valve piston within the sleeve (27) corresponds to the effective diameter of the valve piston at the valve seat (32).
2. Injector according to Claim 1, characterized in that the sleeve (27) is held with radial play in the valve chamber (23).
3. Injector according to Claim 2, characterized in that the control chamber (18) is connected to the valve chamber (23) via a discharge duct (21) with a discharge throttle (22), and in that the discharge duct (21) opens into the valve chamber (23) in a region between a valve chamber inner wall (39) and the sleeve (27).
4. Injector according to one of the preceding claims, characterized in that the actuator (40) is a solenoid drive having at least one solenoid (41) and having at least one armature plate (46) which acts with the latter.
5. Injector according to Claim 4, characterized in that the armature plate (46) is operatively connected to a pressure rod (47), the free end of which (48) which faces away from the armature plate (46) being centred at the end of the valve piston (26) which faces the armature plate (46).
6. Injector according to Claim 5, characterized in that the centring is implemented by means of a concave/convex pairing between the valve piston (26) and pressure rod (27).
7. Injector according to one of Claims 4 to 6, characterized in that the armature plate (42) is subjected to spring force in the direction of the valve piston (26) via a biasing spring (51), wherein the spring force of the biasing spring (51) is weaker than the spring force of the spring (29) within the valve chamber.
8. Injector according to one of Claims 5 to 7, characterized in that the solenoid (41) of the solenoid drive is penetrated by a stop sleeve (49) with a stop face (56) for the armature plate (42), wherein the pressure rod (47) is guided in an axially displaceable fashion within the stop sleeve (49).
9. Injector according to one of the preceding claims, characterized in that the bottom face (33) of the valve chamber (23) is formed by a throttle plate (5).
10. Injector according to Claim 9, characterized in that a connecting duct (35), which is part of a connecting line which supplies low pressure to the front side of the valve piston (26) which faces away from the valve seat (32), in particular connects hydraulically to the low-pressure space (25) and/or a return line, is provided within the throttle plate (5).

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