EP1948922B1 - Optimized armature assembly guidance for solenoid valves - Google Patents

Abstract

The invention relates to a fuel injector having a solenoid valve which actuates a multi-part armature assembly. The armature assembly comprises an armature bolt, an armature bolt which is acted on by a valve spring, and an armature plate. As a result of the lifting motion of the armature bolt, a closing element is opened or closed, whereby an injection valve member can be actuated, in order to relieve the pressure in a control space. The armature plate is guided, decoupled from the armature bolt, on an armature guide.

Description

State of the art

DE 196 50 865 A1 describes a solenoid valve for controlling the fuel pressure in a control chamber of an injection valve, such as a common rail injection system. About the fuel pressure in the control chamber, a stroke movement of a valve piston is controlled, with which an injection port of the injection valve is opened or closed. The solenoid valve comprises an electromagnet, a movable armature and a valve member which is moved with the armature and acted upon by a valve closing spring in the closing direction and which cooperates with the valve seat of the magnet valve and thus controls the fuel drain from the control chamber.

It is known a common rail injector with a two-piece anchor, which is attracted by a solenoid valve. The armature exerts the closing force on a valve ball in the currentless case. When the electromagnet is energized, the armature moves upwards by the armature stroke, the closing force of the closing force acting on the valve ball becomes 0 and an outflow valve opens. An armature guide, which is bolted firmly in the injector body of the fuel injector, receives the anchor bolt. On the anchor bolt, the anchor plate is guided, which in turn is attracted by the electromagnet. The anchor bolt may tip over due to the guide clearance in the anchor guide. The anchor plate in turn may tilt on the anchor bolt, so that the overall tilt of the anchor bolt / anchor plate assembly with respect to e.g. to determine the injector main axis as the sum of the leading games.

The anchor plate has a defined overtravel stop on the armature guide, which removes the kinetic energy of the movement of the armature after the electromagnet is switched off the system. When the valve ball hits its seat, the anchor bolt is stopped in its movement. The anchor plate can still fly to the overstroke (ballistic operating phase) before it hits the overstroke stop. Thus only part of the kinetic energy from the movement of the anchor bolt are reduced in the valve seat. The part of the kinetic energy from the anchor plate is dissipated in the injector body.

In the case of current series products, the problem arises that the valve spring exerting a closing force on the anchor bolt introduces lateral force components into the assembly of anchor plate and anchor bolt. Due to the guiding play between the armature guide and the anchor bolt, this leads to a tilting of the anchor bolt in the armature guide. With strong lateral force, this tilt can also be present in the upper position of the anchor bolt when energized electromagnet, since an anchor bolt stop can rest on one side. Thus, part of the set armature stroke, i. the movement of the anchor bolt in operation, not fully utilized. This leads to a lower injection quantity of fuel into the combustion chamber of an internal combustion engine. Added to this is the friction of the anchor bolt in the anchor guide, which also influences the movement of the anchor bolt. This friction increases with a larger tilt angle α, since the lever arm of the triggering force also increases. The point of application of the valve spring has a relatively large distance to the upper end of the armature guide. This creates at the top and at the bottom of the anchor guide very high punctually acting forces on the anchor bolt, which increase the friction and thus slow the movement of the anchor bolt. The speed at which the anchor bolt moves, i. the opening and closing of the valve ball has a very large influence on the injection quantity introduced into the combustion chamber of the internal combustion engine.

To cope with this problem, the leadership game has been limited in trials, with the aim of reducing the tilt angle. A restriction of the guide play in turn meant that the anchor bolt does not maintain a consistent position in the operation, but takes a different position from injection to injection. This is accompanied by changing friction between anchor bolt and armature guide and thus a scattering of injection quantities.

Furthermore, it has been found that by the above-described total tilting of the armature plate and the anchor bolt to the tilt angle α relative to Injektorhauptachse a collision between armature plate and magnetic core can occur with small residual air gaps between armature plate and magnetic core and on the other hand with unevenly extending residual air gap also uneven Magnetic force distributed on the circumference occurs. This reinforces the random friction forces and thus has an impact on the realized with the fuel injector injection quantities of fuel into the combustion chamber of the internal combustion engine. In addition, the unevenly distributed leads Magnetic force also to a bending of the anchor bolt and thus to a poorer armature guidance, since form higher Reibkraftanteile.

Disclosure of the invention

The object of the present invention is therefore to eliminate the disadvantages inherent in the solutions of the prior art and to provide an armature guide of a multi-part armature assembly for a solenoid valve actuating a fuel injector which fully exploits the stroke of the armature pin and tilts the armature assembly with respect to the main axis eg a fuel injector minimized. For this purpose, the invention proposes, in a two-part anchor assembly comprising an anchor bolt and an anchor plate to equip the anchor plate with an independent anchor bolt guide and to move the distance of the force application point of a valve spring of the solenoid valve on the anchor bolt to the upper end of an anchor guide. As a result, the distance between the point of application of the valve spring to the upper end of the armature guide is considerably shortened. This has the consequence that the transverse forces occurring within the armature guide are reduced at the same lateral forces of the spring, whereby the friction between the anchor bolt and this surrounding armature guide is significantly reduced. The tilting is considerably reduced with the same leadership game between the elongated armature guide and the anchor bolt. Another advantageous effect of the proposed solution according to the invention is to be seen in that the lever arm, which is adjusted by tilting, is significantly reduced, which also contributes to a reduction of friction between the two-piece anchor assembly, in particular the anchor bolt and this surrounding armature guide ,

Due to the decoupled guidance of the anchor plate from the anchor bolt, the maximum tilt of the anchor plate is reduced. Magnetic forces acting unevenly on the armature plate of the two-part armature assembly can be applied to the armature plate guiding outside of the armature guide and thus do not contribute to a bending of the armature bolt, which is enclosed by the inventively proposed elongated armature guide at. Due to the reduction of the transverse forces acting on the anchor bolt, the anchor bolt is easier to move with respect to the elongated armature guide, so that reproducible injection quantities can be achieved, since due to the minimization of the transverse forces, a more smooth guidance of the anchor bolt in the elongated armature guide enclosing the latter can be achieved is. The elongated armature guide, which surrounds the anchor bolt of the armature assembly formed in two parts, on the one hand improves the ease of movement of the anchor bolt movement within the armature guide due to the achievable reduction of the transverse forces, on the other hand, the elongated armature guide provides the leadership for the armature plate of the multi-part armature assembly. Due to the guidance of the anchor plate on the outer lateral surface of the elongated armature guide, transverse forces induced by the anchor plate do not act on the anchor bolts which are movable within the armature guide and impede its movement, but are absorbed by the outer lateral surface of the elongated armature guide.

drawing

Figur 1

den Einfluss des Führungsspiels zwischen Ankerbolzen und einer gemäß des Standes der Technik ausgeführten Ankerführung sowie die vergrößert darge- stellte Verkippung des Ankerbolzens relativ zur Ankerführung,

Figur 2

einen Schnitt durch ein Magnetventil, welches mit der erfindungsgemäßen An- kerbaugruppe sowie der verlängerten Ankerführung versehen ist,

Figur 3

die Einzelteildarstellung der verlängert ausgebildeten Ankerführung,

Figur 4

die Draufsicht auf eine Ankerplatte einer mehrteilig ausgebildeten Ankerbau- gruppe und

Figur 5

den in Figur 4 dargestellten Schnittverlauf V-V durch die Ankerplatte.

With reference to the drawing, the invention will be described below in more detail.
It shows:

FIG. 1

the influence of the guide clearance between the anchor bolt and an armature guide designed according to the prior art and the enlarged representation of tilting of the anchor bolt relative to the armature guide,

FIG. 2

a section through a solenoid valve which is provided with the anchor assembly according to the invention and the extended armature guide,

FIG. 3

the single part representation of the elongated armature guide,

FIG. 4

the top view of an anchor plate of a multi-part Ankererbau- group and

FIG. 5

the in FIG. 4 illustrated section VV through the anchor plate.

embodiment

The representation according to FIG. 1 is an enlarged view of the influence of the guide clearance between an anchor bolt whose armature plate is not shown, and an anchor guide according to the prior art can be seen.

FIG. 1 shows an anchor bolt 10 which is enclosed by an armature guide 12. The anchor bolt 10 is acted upon by a valve spring 24. Between the upper annular surface of the armature guide 12 and the force application point of the valve spring 24 is a distance 22. The transverse forces between the anchor bolt 10 and the armature guide 12th arise, decrease with decreasing distance 22. According to the in FIG. 1 illustrated configuration prevails between the outer circumferential surface of the anchor bolt 10 and the inner circumferential surface of the armature guide 12, a guide clearance 18. In FIG. 1 the anchor bolt 10 is shown in a tilting angle α shown with respect to an injector main axis 14. In the FIG. 1 tilting shown on an enlarged scale causes an inclination of the anchor bolt 10 within the armature guide 12 enclosing this, so that a binding of the anchor bolt 10 due to the friction occurring at the armature guide 12, and an unused Ankerhubweg ΔAH occurs. The unused Ankerhubweg .DELTA.AH can not be exploited in the lifting movement of the anchor bolt 10 relative to the stationary armature guide 12 and does not contribute to the stroke of the anchor bolt 10 and thus not to the opening movement of a valve body to be opened or closed.

The lever arm, which leads to the fact that with the tilting of the anchor bolt 10, an unused Ankerhubweg .DELTA.AH arises between the axis of symmetry of the anchor bolt 10 and the outer end of its abutment surface 38 and is designated by reference numeral 16.

In the illustration according to FIG. 2 is a section through a fuel injector actuated solenoid valve with the inventively proposed armature assembly and an elongated armature guide shown.

In the injector body 30 of a fuel injector is a solenoid valve, which comprises an electromagnet 32. Below the electromagnet 32 is a two-piece anchor assembly comprising the anchor bolt 10 and an anchor plate 70. The anchor bolt 10 is enclosed by an elongated armature guide, 28. The anchor plate 70 is guided on the outer circumferential surface of a neck 29 of the elongated armature guide 28. The anchor bolt 10 is acted upon by the valve spring 24. The distance of the force application point of the valve spring 24 and the top of the upper end of the elongated armature guide 28 is indicated by reference numeral 54 and considerably shorter than that in FIG. 1 illustrated distance 22 between the force application point of the valve spring 24 and the armature guide 12 shown there according to the prior art.

The anchor plate 70 as shown in FIG FIG. 2 is biased by an anchor plate spring 36, which in turn is supported on a disk-shaped receptacle 66 of the elongated armature guide. The disc-shaped receptacle 66 of the elongated armature guide 28 is by means of a clamping screw 52 on a previously screwed into the injector body 30 shim 56 and thus fixed in the injector body 30. About the shim 56, which may be, for example, a classified shim, the Ankerhubweg is defined.

The movement of the anchor plate 70 is bounded above by an adjusting ring 34 which is supported on the anchor bolt 10. At the opposite end of the adjusting ring 34 of the anchor bolt 10 is a disc-shaped stop 38 of the anchor bolt 10, which abuts against the lower end face of the disc-shaped receptacle 66 of the elongated armature guide 28. The disc-shaped stop 38 of the anchor bolt 10 is enclosed by the classified adjustment ring 56. The classified adjusting ring 56 in turn rests on an end face 58 of an injection valve member guide 59. Within the injection valve member guide 59, a control chamber 48 is formed, which is pressurized with fuel under high pressure via an inlet throttle 50 and via a discharge throttle 46 is depressurized. The outlet throttle 46 can by a closing element 42, which in the in FIG. 2 illustrated embodiment is spherical, released or closed. In the injection valve member guide 59, a seat 44 is formed for the here spherically formed closing element 42 in the region of the outlet throttle 46. The ball-shaped closing element 42 is enclosed by a guide body 40, which is subjected to force by the lower end of the anchor bolt 10.

When pressure relief of the control chamber 48 upon opening of the ball-shaped closure member 42 after actuation of the electromagnet 32, a pressure reduction in the control chamber 48 and thereby the opening of the needle-shaped injection valve member 60. This injection openings are opened at the bottom of the fuel injector shown here only partially, so that under high pressure fuel at the combustion chamber end of the fuel injector can be injected into the combustion chamber of the internal combustion engine.

From the illustration according to FIG. 2 shows that the distance 54 between the point of force application of the valve spring 24 and the top of the extended armature guide 28 can be significantly shortened by the extended version of the armature guide 28, so that the introduction of lateral forces by the valve spring 24 with respect to the anchor bolt 10 crucial is reduced. Furthermore is FIG. 2 can be removed that the anchor plate 70 is now - in contrast to solutions according to the prior art - not on the anchor bolt 10, but on the outer circumferential surface of the neck 29 of the elongated armature guide 28 is added. Any tilting of the anchor plate 70 with respect to the axis of symmetry of the anchor bolt 10 will occur not transferred to the anchor bolt 10 due to this storage, but absorbed by the neck 29 of the elongated armature guide 28.

For the sake of completeness it should be mentioned that the injection valve member guide 59 is connected by the clamping screw 52 to a seat 62 fixed to the injector body 30 of the fuel injector.

From the in FIG. 3 shown part drawing of the elongated armature guide shows that the elongated armature guide 28, in connection with FIG. 2 already mentioned disc-shaped receptacle 66 and has an axially extending neck portion 29. Its outer circumferential surface serves as a guide surface 72 for in FIG. 3 anchor plate 70, not shown, of the two-part anchor assembly. In addition, an overstroke stop 74 for the anchor plate 70 is executed on the upper end side of the neck portion of the elongated armature guide 28. The overstroke stop 74 of the elongated armature guide 28 cooperates with a complementary stop on the armature plate 70 (see sectional view according to FIG FIG. 5 ).

While the outer circumferential surface of the neck portion of the elongated armature guide 28 serves as a guide surface 72 for the anchor plate 70, the inner circumferential surface of the elongated armature guide 28 forms a guide surface 68 for the in FIG. 3 also not shown, however FIG. 2 Removable anchor bolt 10. By extending the armature guide 28 in the axial direction is achieved that guided on the guide surface 68 of the elongated armature guide 28 anchor bolt 10 as shown in FIG FIG. 2 is guided over a larger axial length within the armature guide 28 and the tilting of the anchor bolt 10 due to the guide clearance 18 is reduced solely because of this circumstance. As a result of the reduced tilting, the unused armature lifting travel ΔAH is also reduced since this is in direct geometric connection to the tilting.

The representation according to FIG. 4 is an anchor plate to be taken with VV, as in FIG. 5 shown.

The representations according to the FIGS. 4 and 5 is removable, that an anchor plate 70, which on the in FIG. 2 shown anchor bolt 10 is received, wing-shaped and in the embodiment according to FIG. 4 includes three wings. From the sectional view according to FIG. 5 It can be seen that the anchor plate 70 in turn has an overstroke stop 80 which coincides with the overstroke stop 74 at the upper end of the elongated armature guide 28 as shown in FIG FIG. 3 interacts. In addition, on the inside the armature plate 70, a guide surface 78 is formed, which with the outer circumferential surface of the elongated armature guide 28 as shown in FIG FIG. 3 , see. there reference numeral 72, cooperates. Depending on the quality of manufacture and the roundness between the guide surface 78 on the inner side of the anchor plate 70 and the machining quality of the guide surface 72, ie the outer lateral surface of the elongated armature guide 28, a highly accurate guidance of the armature plate 70 on the extended armature guide 28 can be achieved. In order to move the anchor bolt 10 against the action of the valve spring 24 upwards, the magnetic force acting on the anchor plate 70 as a tensile force is transmitted via a transfer surface 82 in the adjustment ring 34 and thus to the anchor bolt 10.

The elongated armature guide 28 has the task of guiding the anchor bolt 10 inside and to provide a receptacle in the injector. The overstroke stop 74 on the elongated armature guide 28 shifts upward. The function of the guide of the anchor plate 70 is the proposed solution according to the invention now not taken over by the anchor bolt 10, but by the elongated armature guide 28. For this purpose, the extended armature guide 28 has the additional functional surface on the outer diameter in the form of the guide surface 72. The armature plate 70 has the function of receiving the magnetic force generated by the electromagnet 32 and transmitting it via the transfer surface 82 to the adjusting ring 34 and thus to the armature bolt 10 for opening the valve, the guide surface 78 on the outer circumferential surface, i. the guide surface 72 of the extended armature guide 28 to transmit the opening force on the anchor bolt 10 and provide an overstroke, namely the overstroke stop 80. The guide of the anchor plate 70 is in contrast to previously known from the prior art solutions not on the anchor bolt 10 directly, but is laid in the proposed solution according to the invention on the extended anchor guide 28 and the neck area. Thus, the inner diameter of the guide of the anchor plate 70 increases, wherein the guide is given by the guide surface 72 at the neck region of the elongated armature guide 28 and by the guide surface 78 on the inside of the neck 29 of the anchor plate 70.

Claims (9)

1. Fuel injector having a solenoid valve which actuates a multi-part armature assembly comprising an armature bolt (10) acted on by a valve spring (24), comprising an armature plate (70) and comprising an armature guide (28), and by means of a stroke movement of the armature bolt (10), a closing element (6) is opened in order to release the pressure of a control chamber (48) or is closed, whereby an injection valve member (60) can be actuated, characterized in that the armature plate (70) is guided, decoupled from the armature bolt (10), on the armature guide (28).
2. Fuel injector according to Claim 1, characterized in that an end side, which serves as an overstroke stop (74), of the armature guide (28) is situated at a reduced distance (54) from the force introduction point of the valve spring (24).
3. Fuel injector according to Claim 1, characterized in that the armature plate (70) is guided on a guide surface (72) of the armature guide (28).
4. Fuel injector according to Claim 1, characterized in that the armature plate (70) has a transmission surface (82) for transmitting the magnet force to the armature bolt (10).
5. Fuel injector according to Claim 1, characterized in that the armature plate (70) is preloaded by a spring element (36) which is held between a sleeve-shaped extension of the armature plate (70) and a disc-shaped receptacle (66) of the armature guide (28).
6. Fuel injector according to Claim 1, characterized in that a guide play (18) is present between the armature guide (28) and the armature bolt (10) and the tilting α of the bolt (10) in relation to an injector main axis (14) of the fuel injector is minimized by the elongation of the armature guide (28) in the axial direction.
7. Fuel injector according to Claim 1, characterized in that a guide surface (72) on the outer lateral surface of the armature guide (28), a guide surface (78) of the armature plate (70) and an inner peripheral surface (68) of the armature guide (28) are formed with increased surface quality.
8. Fuel injector according to Claim 3, characterized in that the guide surface (72) is a guide, which is positionally fixed in relation to the injector body (30) and independent of the movement of the armature bolt (10), for the armature plate (70).
9. Fuel injector according to Claim 1, characterized in that the armature guide (28) has an elongated throat section (29), such that lateral forces between the armature bolt (10) and the armature guide (28) are minimized.

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