DE102007058766A1 - Control valve for a fuel injector - Google Patents

Abstract

The control valve has an axially-mobile valve shell (20) pressing on a valve seat (30) and operated by an electromagnetic setting element (14). The seat separates the low pressure chamber (31), connected by an outflow channel to a return line (35), from the high pressure chamber. The shell has a magnetic armature (22) in a cavity (33). There is a hydraulic connection between the outflow channel and the armature cavity.

Description

The The invention relates to a force-balanced control valve for a fuel injector having the features of the preamble of Claim 1.

State of the art

servo-controlled Fuel injectors for common rail systems with a essentially leak-free nozzle needle side have due a lack of low pressure stage a very short delay time between control and injection. To such fuel injectors both a zero quantity and a platinum-free quantity map To realize meaningful, is a fast switching Solenoid valve required. For this reason, solenoid valves balanced in terms of force or pressure, d. h., that the to be switched rail pressure no resulting pressure force on a Valve piston of the solenoid valve exercises. The majority the force potential of the solenoid valve can thus for the Dynamics are provided for switching and does not have to be considered closing force be kept for the control valve.

Solenoid valves, for switching servo circuits of fuel injectors are used, usually have a certain low pressure dependence. Just the said pressure balanced solenoid valves operate at a low static force level and are therefore particularly sensitive against external forces. The low pressure dependence is mainly due to the outflowing tax when opening the solenoid valve justified, the one Pressure wave in the low pressure circuit triggers. Due to the pressure oscillations arise especially at the armature surfaces of the solenoid valve great hydraulic forces that greatly increase the switching characteristics influence. The genesis, spread and strength of Pressure waves in a two-phase flow of gas and air, as it prevails in the valve space or return are not deterministic and are subject to strong fluctuations. The high gas content in the return is mainly due to the cavitating outlet throttle founded.

A fuel injector with a force-balanced control valve actuated by a solenoid actuator, which serves to control the pressure in a hydraulic control chamber and has a valve piston with a flat seat, is off EP 1 639 563 A2 known. When the control valve is open, the hydraulic control chamber, which communicates with a high-pressure port via an inlet throttle, is connected to a low-pressure port, whereby the pressure in the hydraulic control chamber drops. As a result, the opening force acting on a pressure shoulder of the nozzle needle of the injection valve member exceeds the closing force emanating from the control chamber. The nozzle needle is lifted from a nozzle needle seat and injected fuel at the system pressure of the common rail in the combustion chamber of an internal combustion engine.

To improve the dynamic behavior of a force balanced control valve was already in DE patent application 10 2007 001 554.4 proposed to derive the Absteuermenge from the hydraulic control chamber via a guided through the valve piston axial bore and not an armature space of the magnetic actuator in the low-pressure connection.

task It is the object of the present invention to provide a force balanced control valve to create for a fuel injector that is going through an extremely high robustness and a lower low-pressure dependence distinguished.

Presentation of the invention

The The object of the invention is with the characterizing measures of claim 1.

Thereby, that during the switching operation of the armature of the fuel is sucked from the armature space in the low-pressure connection, arises in the anchor space a low pressure level. Because of this will be one Hydraulic bonding of the armature on the stroke stop during the closing of the Air gap prevents, because in the entire armature space, a negative pressure prevails and no pressure difference between anchor top and Anchor bottom can occur, even if not by the closing movement on the stroke stop as a result of a squish gap, a negative pressure is created. On the other hand it prevents one from the Absteuermenge the control chamber conditional pressure increase only one side of the armature is present and so a parasitic force on the armature acts.

advantageous Further developments of the invention are by the measures the dependent claims possible.

It is particularly advantageous to generate a suction effect in the armature space via the hydraulic connection. For this purpose, a flow constriction is formed in the outflow, in which the hydraulic connection opens. The suction from the armature space is advantageously realized by means of a differential pressure method. For this purpose, the flow constriction has the function of a Venturi nozzle, so that due to the pressure reduction resulting from the increased flow velocity in the flow constriction, an effective pressure is created by the hydraulic connection Fuel is sucked out of the armature space out into the outflow channel.

According to one Embodiment of the control valve is the discharge channel from a through hole formed in the valve sleeve realized, wherein the flow constriction as diameter constriction the through hole is formed. It is also possible to insert into the through hole an insert in which the Diameter constriction is formed.

According to one Another embodiment of the control valve is the discharge channel formed by an annular gap, one inserted into the through hole Pressure pin surrounds. The flow constriction is here formed by a pin formed by the narrowed annular gap. The pressure pin limits this with a control room-side end face the high pressure side valve chamber. The annulus is over one guided by the wall of the valve sleeve Transverse bore with the low pressure side valve chamber hydraulically connected.

Conveniently, is the valve sleeve on the outer circumference in one a housing part formed guide axially movably guided, whereby the guidance the anchor space limited. It is also appropriate if between magnet armature and a magnetic assembly of the actuator arranged a stop plate for forming a residual air gap is. Because the valve sleeve is an extension having, with the valve sleeve in an adjacent spring chamber protrudes, forms between spring chamber and extension a hydraulic throttle that stays out permanently over the entire Stroke of the valve sleeve acts.

embodiments

The Embodiments of the invention are in the drawing shown and in the following description in more detail explained.

It demonstrate:

1 a control valve side section of a fuel injector according to a first embodiment and

2 a control valve side section of a fuel injector according to a second embodiment.

The as a cut in the 1 and 2 shown fuel injector has an injector 11 with several housing parts 11.1 to 11.4 , a nozzle needle 12 , a control valve 13 and a magnetic actuator 14 as an actuating element. The nozzle needle 12 belongs to a known injection valve member, is injected via the fuel into the combustion chamber of an internal combustion engine. The fuel is provided via a fuel high-pressure accumulator, not shown, (common rail) of a diesel injection device.

In the housing part 11.1 is the nozzle needle 12 guided and a hydraulic control room 15 formed, with the nozzle needle 12 with a printing surface 16 the control room 15 is exposed. In the control room 15 leads an inlet bore 17 with an inlet throttle, wherein the inlet bore 17 is connected to a high pressure port of the high pressure fuel storage, not shown.

The control valve 13 has a valve sleeve 20 with a plate-shaped magnet armature 22 and a through hole 23 on. The valve sleeve 20 is in a pilot hole 24 in the housing part 11.3 hydraulically tight and is guided by a valve spring 25 with a ring surface 26 against a sealing surface 27 pressed. Between ring surface 26 and sealing surface 27 a valve seat forms 30 out. The ring surface 26 is in the embodiment in 1 on the valve sleeve 20 ground outside, leaving the valve seat 30 outside of the valve sleeve 20 lies. The sealing surface 27 is at one of the housing part 11.2 trained valve plate 29 trained.

The valve seat 30 separated a low pressure side valve chamber 31 from a high pressure side valve chamber 32 , The through hole 23 stands with the low-pressure side valve chamber 31 hydraulically connected and forms a discharge channel 41 in a spring room 34 flows, in turn, via a return line 35 is hydraulically connected to a low pressure / return system, not shown. The high pressure side valve chamber 32 is over a drain hole 37 with a drain throttle with the control room 15 hydraulically connected. At the plate-shaped magnet armature 22 is the valve sleeve 20 from an anchor room 33 surround.

In the housing part 11.4 is the magnetic actuator 14 arranged with a magnetic assembly, which is a magnetic coil 18 and a magnetic core 19 comprising, wherein the magnetic assembly, the magnetic force for the armature 22 generated. At the magnet assembly-side end face of the magnet armature 22 is a stop disc 36 disposed between the magnet assembly and the magnet assembly side end face of the magnet armature 22 sets a residual gap. This residual air gap is intended to prevent the magnet armature 22 sticking when the magnetic module is deactivated. Between the magentankerseitigen face of the magnet assembly and the stopper disc 36 lies in the closed state of the valve seat 30 a gap that coincides with the armature stroke of the valve sleeve 20 He narrows until he hits the stop disc 36 at the Ma power assembly is closed. The gap thus forms a function of the armature stroke of the valve sleeve 20 adjustable hydraulic throttle 45 out.

In the embodiment in 1 is in the through hole 23 the valve sleeve 20 an insert 38 with a diameter restriction 39 arranged. The diameter restriction 39 forms inside the through hole 23 a flow constriction 40 out. From the diameter restriction 39 branches a hydraulic connection 42 starting at the outer surface of the valve sleeve 20 in the anchor room 33 empties. The diameter restriction 39 forms together with the hydraulic connection 42 a Venturi nozzle, whose effect later in connection with the function of the control valve 13 is described. The flow constriction 40 for forming the Venturi nozzle can in the embodiment according to 1 in the through hole 23 be incorporated. But it is also in 1 shown execution possible, namely the use 38 with the diameter narrowing 39 as a separate component in the through hole 23 use.

According to the embodiment 1 is the low-pressure side valve chamber 31 in the through hole 23 inside the valve sleeve 20 , The high pressure side valve chamber 32 that with the control room 15 over the drain hole 37 is connected as an annular chamber outside the valve sleeve 20 arranged.

According to the embodiment 2 is in the through hole 23 the valve sleeve 20 a pressure pin 51 with a control room-side end face 52 and a support surface 53 arranged. The bearing surface 53 is supported on a support surface serving as an abutment 54 on the housing part 11.4 from. The pressure pin 51 is with a cylinder section 55 in the through hole 23 hydraulically tight. Then to the cylinder section 55 is the pressure pin 51 with a first bolt-shaped section 56.1 and a second bolt-shaped portion 56.2 executed. Between the bolt-shaped sections 56.1 and 56.2 is a cone shape section 57 arranged. In addition, between the lateral surfaces of the bolt-shaped sections 56.1 and 56.2 and the through hole 23 the valve sleeve 20 a first annular gap 58.1 and a second annular gap 58.2 educated. Between the annular gaps 58.1 and 58.2 is the cone shape section 57 , which form an inverse form of a Venturi nozzle, so that through the conical section 57 between the two annular gaps 58.1 and 58.2 a narrowed annular gap 59 arises, the flow constriction 40 formed. In the area of the narrowed annular gap 59 one opens through the valve sleeve 20 guided hydraulic connection 62 in the anchor room 33 leads.

For the formation of the valve seat 30 is in the embodiment in 2 the sealing ring surface 26 at the inner diameter of the valve sleeve 20 ground in. In contrast to the embodiment in 1 is the high pressure side valve chamber 32 inside the valve sleeve 20 educated. The high pressure side valve chamber 32 is from the control room side end face 52 of the pressure pin 51 limited. The low-pressure side valve chamber 31 surrounds the valve sleeve from the outside 20 in the guide-free section near the valve seat 30 , Through the wall of the valve sleeve 20 is still a connection hole 63 , led, which is the low-pressure side valve chamber 31 with the annular gap 58.1 combines.

The embodiment in 2 differs further from the embodiment in 1 in that the valve sleeve 20 an extended section 65 which is in the spring chamber 34 by means of a guide gap 66 protrudes. The guide gap 66 forms a second hydraulic throttle 67 out. The drain hole 37 is also through the valve plate 19 guided and connects the control room 15 with the inside of the valve sleeve 20 formed high pressure side valve chamber 42 , In addition, in the embodiment in 2 the spring chamber 34 via a connection channel 69 with the return line 35 connected.

According to the embodiment 2 the Venturi nozzle is designed as an annular nozzle, wherein the into the through hole 23 inserted pressure pin 51 is shaped accordingly. In addition, that of the stroke of the magnet armature 22 influenced throttle 45 through the permanent throttle 67 extended. In this way, the refilling of the anchor space 33 be delayed.

In the fuel injector according to 1 and 2 is activated by actuation of the magnetic actuator 14 the magnet armature 22 with the valve sleeve 20 using the magnetic force of the magnet assembly from the valve seat 30 lifted. This will cause the high-pressure side valve chamber 32 with the low pressure side valve chamber 31 hydraulically connected. Since the low-pressure side valve chamber 31 permanently with the return line 35 communicates with the valve seat open 30 over the drain hole 37 also the control chamber pressure relieved. This results in a force acting in the opening direction opening force on the nozzle needle on a pressure shoulder, not shown 12 that is larger than the one in the control room 15 acting closing force. The nozzle needle 12 is opened, thereby injecting fuel with the system pressure provided by the fuel high-pressure accumulator system in the combustion chamber of the internal combustion engine.

Also in the open state is the valve sleeve 20 pressure balanced, because the low pressure side valve chamber 31 over the through hole 23 with the spring chamber connected to the low pressure 34 hydraulically connected. Thus lies at the bottom and at the top of the valve sleeve 20 almost the same pressure level. Advantageously, the diameter of the spring chamber 34 slightly larger than the outer diameter of the valve sleeve 20 to the pressure drop across the flow constriction 40 compensate.

By the Venturi nozzle principle working flow constriction 40 becomes the static hydraulic pressure in the through hole 23 greatly reduced, so that due to the greater flow velocity at the narrowest point, a negative pressure is created, via the hydraulic connections 42 . 62 Fuel from the anchor room 33 sucks, causing the armature space 33 is almost evacuated. The suction is facilitated by the fact that the armature 22 when opening strikes the magnet assembly, causing the armature space 33 from the spring chamber 34 that is permanently with the return 35 is connected, hydraulically disconnected. The anchor room 33 can not be refilled from the low pressure / reflux system. Through the extraction and the hydraulic decoupling of the armature space 33 from the spring chamber 34 becomes a pressure difference at the upper and lower end faces of the plate-shaped armature 22 , which is justified either by the outflowing control amount or a hydraulic gluing avoided.

Will the magnetic actuator 14 deactivated, the magnetic force collapses and the valve sleeve 20 is through the valve spring 25 back in the valve seat 30 posed. With increasing stroke of the valve sleeve 20 becomes the throttle 45 between magnet armature 22 and magnet assembly open and the armature space 33 will be back from the spring chamber 34 filled with fuel.

The valve sleeve 20 and the magnet armature 22 can either be made from one piece or the magnet armature 22 is on the valve sleeve 20 pressed or riveted. The armature stroke is via the magnet assembly or via the stop disc 36 limited. The residual air gap is with the stop disc 36 set, which consists of a non-magnetic material. But it is just as possible on the stop disc 36 to dispense with and instead of the magnet assembly-side end face of the armature 22 to be provided with a chromium layer.

QUOTES INCLUDE IN THE DESCRIPTION

This list The documents listed by the applicant have been automated generated and is solely for better information recorded by the reader. The list is not part of the German Patent or utility model application. The DPMA takes over no liability for any errors or omissions.

Cited patent literature

• - EP 1639563 A2 [0004]
• - DE 102007001554 [0005]

Claims (10)

Control valve for a fuel injector with a valve sleeve ( 20 ), which is guided axially movable and with a closing force against a valve seat ( 30 ), whereby the valve sleeve ( 20 ) of an electromagnetic actuator ( 14 ) is operable, wherein the valve seat ( 30 ) a low pressure side valve chamber ( 31 ) from a high pressure side valve chamber ( 32 ), wherein the low-pressure side valve chamber ( 31 ) via a discharge channel ( 41 ) permanently with a return line ( 35 ) is hydraulically connected, wherein the valve sleeve ( 30 ) a magnet armature ( 22 ), which in an anchor space ( 33 ), which in turn is connected to the return line ( 35 ) is hydraulically connected, and wherein the high-pressure side valve chamber ( 32 via a drain hole ( 37 ) with a control room ( 20 ) for a nozzle needle ( 12 ) of an injection valve member is hydraulically connected, characterized in that between outflow ( 41 ) and anchor space ( 33 ) a hydraulic connection ( 42 . 62 ) is trained. Control valve according to claim 1, characterized in that the outflow channel ( 41 ) a flow constriction ( 40 ) into which the hydraulic connection ( 42 . 62 ) opens. Control valve according to claim 2, characterized in that the flow constriction ( 40 ) forms the function of a Venturi nozzle, so that an effective pressure is created by the hydraulic connection ( 42 . 62 ) Fuel from the armature space ( 33 ) out into the outflow channel ( 41 ) is sucked off. Control valve according to claim 1, 2 or 3, characterized in that the outflow channel ( 41 ) of one in the valve sleeve ( 20 ) formed through-bore ( 23 ) is realized, and that the flow constriction ( 40 ) by a in the through hole ( 23 ) formed diameter constriction ( 39 ) is executed. Control valve according to claim 4, characterized in that in the through-bore ( 23 ) an insert ( 38 ) with the diameter restriction ( 39 ) is used. Control valve according to claim 1, 2 or 3, characterized in that the outflow channel ( 41 ) of an annular gap ( 58.1 . 58.2 ) is formed, one in a through hole ( 23 ) of the valve sleeve ( 20 ) ( 51 ) and that the flow constriction ( 40 ) by one of the pressure pin ( 51 ) formed narrowed annular gap ( 59 ) is formed. Control valve according to claim 6, characterized in that the annular space ( 58.1 ) via a through the wall of the valve sleeve ( 20 ) guided transverse bore ( 63 ) with the low pressure side valve chamber ( 31 ) connected is. Control valve according to one of the preceding claims, characterized in that the valve sleeve ( 20 ) on the outer circumference in a formed on a housing part guide ( 24 ) is guided axially movable, and that the guide ( 24 ) the anchor space ( 33 ) limited. Control valve according to one of the preceding claims, characterized in that between magnet armature ( 22 ) and a magnetic assembly of the actuating element ( 14 ) a stop disc ( 45 ) is arranged to form a residual air gap. Control valve according to one of the preceding claims, characterized in that the valve sleeve ( 20 ) an extension ( 65 ), with which the valve sleeve ( 20 ) in an adjacent spring chamber ( 34 protruding so that between spring chamber ( 34 ) and extension ( 65 ) a hydraulic throttle ( 67 ), which permanently over the entire stroke of the valve sleeve ( 20 ) acts.