WO2014206872A1

WO2014206872A1 - Magnet assembly for a fuel injector

Info

Publication number: WO2014206872A1
Application number: PCT/EP2014/063000
Authority: WO
Inventors: Christian Faltin; Klemens Steinberg
Original assignee: Robert Bosch Gmbh
Priority date: 2013-06-27
Filing date: 2014-06-20
Publication date: 2014-12-31
Also published as: DE102013212504A1; EP3014109B1; EP3014109A1

Abstract

The invention relates to a magnet assembly (3) for a fuel injector (1). The magnet assembly (3) comprises an electromagnet (5) having a magnet core (7) and a magnet coil (9). The magnet assembly (3) further comprises an armature (17) for moving a valve member and a residual air gap disc (25) for setting a spacing between the magnetic core (7) and the armature (17). The residual air gap disc (25) is arranged between the electromagnet (5) and the armature (17). Furthermore, the residual air gap disc (25) is fixed in a direction parallel to a longitudinal axis (35) of the magnet assembly (3) by a fixing element (29). The fixing element (29) is designed as a separate item from the residual air gap disc (25).

Description

description

Magnetic assembly for a fuel! Njector state of the art

A fuel injector for motor vehicles may be a solenoid valve for controlling a fuel pressure in the fuel! have injector or in a control chamber of an injection valve.

By means of the fuel pressure in the control chamber, a lifting movement of a valve piston is controlled, with which an injection opening of the injection valve can be opened or closed. The solenoid valve has an electromagnet and a movable armature. A valve member, which is acted upon by a valve closing spring in the closing direction, is moved with the armature. The valve member cooperates with a valve seat of the solenoid valve and thus controls the fuel drain from the control chamber.

The electromagnet has a magnetic coil and a magnetic core. The anchor has an anchor plate and an anchor bolt. Between the armature plate and the magnetic core, a residual air gap disc (RLSS) may be provided which defines a residual air gap between these elements. In known fuel injectors, the residual air gap disk is arranged floating between the armature and the electromagnet and can be centered over its outer circumference.

When operating the fuel! njektors leads the armature stroke, that is, the tightening and releasing of the armature, in connection with displacement and filling of the gap between the armature and magnetic core with medium, to a more or less pronounced or changing hydraulic bonding or adhesion of the residual air gap disc at anchor or at the magnetic core. As a result, different closing conditions and thus also different closing durations of the armature in injector operation can arise. In turn, these closing duration influences can lead to long-term dispersion of the injection duration and thus to variations in the injection quantity of the fuel! cause njektors. Especially with small injection quantities for a pilot injection, such scattering may be undesirable.

From EP 2 254 130 A2, a residual air gap disk is known, which has projections and is fixed in position over these projections. However, such a design of the residual air gap disc limits the choice of material of the residual air gap disc. Furthermore, wear of the projections can reduce the life of the residual air gap disk.

Disclosure of the invention

There may therefore be a need for an improved magnet assembly for a fuel! Njektor exist for a magnet assembly, which allows in particular a more reliable operation of the fuel injector and less wear.

This need can be met by the subject matter of the present invention according to the independent claims. Advantageous embodiments of the present invention are described in the dependent claims.

In the following, features, details and possible advantages of a device according to embodiments of the invention will be described in detail.

According to a first aspect of the invention, a magnet assembly for a fuel! presented. The magnet assembly includes an armature for moving a valve member and an electromagnet having a magnetic core and a solenoid. Further, the magnet assembly has a residual air gap disk for adjusting a distance between the magnetic core and the armature. The residual air gap disk is arranged between the electromagnet and the armature. In this case, the residual air gap disk is fixed in a direction parallel to a longitudinal axis of the magnet assembly by a fixing element. The fixing element is designed separately from the residual air gap disk. In other words, the idea of the present invention is based on fixing the residual air gap disk in the axial direction with respect to the magnetic core by means of an additional, separately executed fixing element. Thanks to this inventive design of the magnet assembly with a fixing substantially no relative movement between the electromagnet and the residual air gap disc takes place. In particular, the fixing element is arranged between the residual air gap disk and the anchor plate and contributes to the adhesion between the armature or the anchor plate and the residual air gap disk being prevented or stably being pronounced in its strength. In addition, the fixing element can serve to secure the residual air gap disk in a manget sheath of the electromagnet during assembly of the magnet assembly.

With the help of the fixing element more constant closing times of the armature can be ensured in injector operation. In this way, constant injection periods and injection quantities are guaranteed. This is particularly advantageous for small injection quantities, for example in a pre-injection. This will ensure a reliable operation of the fuel! Njektors allows.

In addition, the materials of the residual air gap disk and the fixing element can be chosen freely and independently of each other thanks to the separate configuration. As a result, the Verscheiß the residual air gap disk and also the wear of the fixing can be minimized. In particular, the axial bending deformation of the residual air gap disk is reduced by the armature movement, thereby reducing the wear of the residual air gap disk. Furthermore, the fixing element and the residual air gap disc prevent wear of elements that would touch each other in a configuration without fixing element and residual air gap disc.

The following further advantages result from the use of the separate fixing element: An axial deflection of the armature, that is, the armature stroke, remains the same from switching operation to switching operation. As a result, the fuel injector shows over its lifetime in the closing period a comparable behavior to the new state.

The closing duration of the valve member, which is monitored and corrected by a control unit, can undesirably occur in known magnet assemblies also take into account the variations in the closing time caused by the hydraulic bonding of the residual air gap. In the embodiment of the magnetic assembly according to the invention with the fixing element, such "temporary" corrections can be avoided by the control unit.

Another advantage of the embodiment of the magnet assembly according to the invention can be seen in the fact that the fuel! Njektor or on the magnet assembly no structural changes are necessary. It is merely an additional component, namely the fixing inserted.

The magnet assembly or the fuel injector can be used in a motor vehicle with an internal combustion engine, for example with a diesel engine. The magnet assembly together with the valve member may also be referred to as a solenoid valve and be used to control a fuel pressure in a control chamber of an injection valve, for example in a common rail high-pressure accumulator injection system.

The magnetic core of the electromagnet may surround the magnetic coil. In this case, the magnetic core may have a radially outer pole, also referred to as Magnetkernaußenpol, and a radially inner inner pole, also referred to as Magnetkerninnenpol. The anchor may have an anchor plate and an anchor bolt.

The distance between a surface of the electromagnet and a surface of the anchor plate facing the electromagnet may be referred to as a residual air gap. In this residual air gap, the residual air gap disk is arranged. The residual air gap disk can define the minimum distance between the armature plate and the electromagnet. Furthermore, the residual air gap disc can dampen the armature movement. In particular, the residual air gap disc can be circular or annular. Furthermore, the residual air gap disk comprises or consists of a ferromagnetic or a non-magnetic material. The fixing element fixes the residual air gap disc in a direction parallel to a longitudinal axis, that is, in the axial direction of the magnet assembly or the Fuel! njektors. The axial direction corresponds to the direction of movement of the valve piston of the fuel! njektors.

The fixing element may preferably comprise or consist of a non-magnetic material. For example, the fixing element steel and / or plastic. The fixing element may have the same material as the residual air gap disk. Alternatively, the fixing element has a different material than the residual air gap disk. For example, the fixing element may be designed as a spring, which is biased in the axial direction.

According to one exemplary embodiment of the invention, the fixing element fixes the residual air gap disk such that a rotationally symmetrical introduction of force into the residual air gap disk takes place with respect to the longitudinal axis. That is, the residual air gap disk and the fixing element are each rotationally symmetrical.

According to a further embodiment of the invention, the fixing element fixes the residual air gap disc in a direction perpendicular to the longitudinal axis of the magnet assembly. This means that the residual air gap disc is fixed in both the axial and in the radial direction with respect to the electromagnet. For example, the residual air gap disk can be centered over its circumference and then pressed against the electromagnet by the fixing element. According to a further embodiment of the invention, the fixing element is designed as a parallel to the longitudinal axis of the magnet assembly biased spring element. In this case, a spring element can be an elastically or else partially plastic restoring element which can deform under load and return to the original shape after relief.

For example, the fixing element may be designed as an axially and / or radially resilient spring ring. In one embodiment, as a merely radially resilient spring ring, the fixing element is biased by additional elements on the magnetic sleeve, such as annular grooves or bevels in the axial direction. In a design as an axially resilient spring ring, the defined rigidity of the

Circlip optionally in combination with a built-in Pressing the spring ring exert a desired axial force on the residual air gap disk.

According to a further embodiment of the invention, the fixing element is designed as a spring ring. The spring ring may also be referred to as a plate spring. In this case, the spring ring on an oval, a circular, a trapezoidal or a C- or S-shaped cross-section. The cross section runs parallel to the longitudinal axis of the magnet assembly. According to a further embodiment of the invention, the fixing element is designed as a spiral spring or as a wave spring. In particular, the spring element may be designed as a helical spring or as a torsion spring. In the embodiment as a wave spring, the fixing element can be designed, for example, similar to a multi-layered disc spring. The load or bias of the fixing extends along the spring axis, with the longitudinal axis of the

Magnet assembly coincides.

According to a further embodiment of the invention, the fixing element is designed as a clamping sleeve. In this case, a clamping sleeve can be a solid material element which is pressed or clamped between the residual air gap disk and the anchor plate, for example by way of pressing mass, and / or welded to the magnet sleeve. In this case, the clamping sleeve can be made inelastic. According to a further embodiment of the invention, the fixing element is clamped between the residual air gap disc and the armature, pressed and / or welded. When clamping or pressing in the fixing element can enter into a frictional connection with other elements such as the magnet sleeve or with the anchor plate. In particular, the fixing element may be arranged between the anchor plate and the residual air gap disc such that it is fixed in a self-locking manner. Furthermore, the fixing element can be welded to the magnetic sleeve, for example. For this purpose laser shearing can be used. According to a further embodiment of the invention, the electromagnet is arranged in a magnet sleeve. The magnet sleeve has a clamping element, which is designed to press the fixing element in a direction parallel to the longitudinal axis of the magnet assembly against the residual air gap disc; Alternatively or additionally, the magnet sleeve has a receiving element which is designed to receive an end region of the fixing element and to prevent it from slipping in a direction perpendicular to the longitudinal axis of the magnet assembly.

The clamping element may for example be designed as an inclined plane or as a slope. The inclined plane runs in a plane that includes an angle smaller than 90 ° with the surface of the magnetic core. Alternatively, the clamping element can be designed as a projection or as an annular groove in the magnet sleeve. In addition or as an alternative to the clamping element, the magnetic sleeve has a receiving element, which is designed, for example, as a recess or indentation on the inner circumference of the magnetic sleeve.

According to a further embodiment of the invention, the electromagnet has an inner pole and an outer pole. The residual air gap disk is arranged and fixed in the region of the outer pole. In particular, the residual air gap disk can be referred to as the outer residual air gap disk (aRLSS). The inner pole is the pole closest to the longitudinal axis of the magnet assembly. The outer pole is the pole further away from the longitudinal axis.

Other features and advantages of the present invention will become apparent to those skilled in the art from the following description of exemplary embodiments, which are not to be construed as limiting the invention with reference to the accompanying drawings.

Fig. 1 shows a cross section through a magnet assembly for a fuel injector according to an embodiment of the invention

Fig. 2 shows different embodiments of the fixing as a spring ring

Fig. 3 shows different embodiments of the fixing as a clamping sleeve

Fig. 4 shows an embodiment of the fixing element as a spiral spring FIG. 5 shows further embodiments of the fixing element with different cross sections. All the figures are merely schematic representations of devices according to the invention or of their components according to embodiments of the invention. In particular, distances and size relationships are not shown to scale in the figures. In the various figures, corresponding elements are provided with the same reference numbers.

In Fig. 1 a cross section through a magnet assembly 3 is shown. The magnet assembly 3 is doing a part of a fuel! njektors 1 dar. The magnet assembly 3 can be used as a solenoid valve for controlling a fuel pressure in the fuel! Njektor 1 or be executed in a control chamber of an injection valve. By means of the fuel pressure in the control room is a lifting movement of a

Controlled valve piston with which an injection port of the injector can be opened or closed.

The magnet assembly 3 has an electromagnet 5 and a movable armature 17. The electromagnet 5 is arranged in a magnet sleeve 15 and has a magnetic coil 9 and a magnetic core 7. The armature 17 has an anchor plate 19 and an anchor bolt 21. Between the armature plate 19 and the magnetic core 7, a residual air gap disk 25 is provided, which defines a residual air gap 27 between the electromagnet 5 and the armature 17 and contributes to the damping of the armature movement. The electromagnet 5 has a

Magnetkerninnenpol 11 and a Magnetkernaußenpol 13. The magnetic core inner pole 11 is arranged closer to a longitudinal axis 35 than the Magnetkernaußenpol 13. The residual air gap disk 25 is disposed in the region of Magnetkernaußenpols 13 and can therefore be referred to as external residual air gap disk 25.

In known fuel injectors, the residual air gap disk is freely floating between armature and electromagnet and can adhere alternately to the armature and the magnetic core by so-called hydraulic bonding. This can lead to different closing states and thus also to different closing durations of the armature. This can cause variations in the Injection amount of the fuel injector caused. If the residual air gap disc is executed with projections and fastened by these in order to avoid hydraulic sticking, this limits the choice of material of the residual air gap disc. Furthermore, wear of the projections reduces the service life of the residual air gap disk.

In the embodiment of the magnet assembly 3 according to the invention, an additional separately executed fixing element 29 made of non-magnetic material is provided between the residual air gap disk 25 and the anchor plate 19 or a dial 23 connected to the magnet sleeve 15. The fixing element 29 fixes the residual air gap disk 25 in the axial direction, that is to say in a direction parallel to the longitudinal axis 35 of the magnet assembly 3. This produces a stable or constant state between the armature 17 and the residual air gap disk 25. In other words, mixed states of the residual air gap disk 25 between hydraulic bonding and detachment due to the fixing element 29 are avoided.

In addition to the axial fixation, the residual air gap disk 25 is radially centered by the fixing element 29. Further, the fixing member 29 is designed and arranged on the magnet assembly 3, that a flow of a control and

Return flow in the direction of return 33 (in Fig. 1 upwards) is ensured. That is, the control or return amount, as in previous magnetic assemblies in the center of the magnetic core 7 along the valve spring 31 and also between the magnetic sleeve 15 and the outer circumference of the magnetic core 7 run off, without being hindered by the fixing member 29.

In Figs. 2 to 5 are cutouts of the magnet assembly 3 are shown. 2 to 5 show different embodiments of the fixing element 29. In FIGS. 2A to 2D, the fixing element 29 is designed as a spring ring with different cross sections. Furthermore, the magnetic sleeve 15 in FIGS. 2A to 2D has different geometrical clamping features or clamping elements 37 for pressing the fixing element 29 against the residual air gap slide 25.

In FIG. 2A, the fixing element 29 is designed as a spring ring with an oval cross-section. In this case, a clamping element 37 designed as an annular groove is provided in the magnet sleeve 15. The spring ring is arranged in the annular groove, in that it presses the residual air gap disk 25 in the axial direction against the magnetic core outer pole 13. In Fig. 2B, the fixing member 29 is similar to the embodiment in Fig. 2A executed. In contrast to FIG. 2A, the spring ring in FIG. 2B has a round or circular cross-section parallel to the longitudinal axis 35. The spring ring is positioned self-locking on the annular groove as in FIG. 2A.

In Fig. 2C, the fixing element 29 is also designed as a spring ring with a circular cross-section. In contrast to Fig. 2B, the clamping member 37 is executed in Fig. 2C as an inclined plane which forms an angle <90 ° with the surface of the magnetic core 7 and in this way the spring ring against the

Residual air gap disk 25 presses. Fig. 2D shows a similar to Fig. 2C embodiment of the clamping feature 37 as an inclined plane. In contrast to FIGS. 2A to 2C, the fixing element 29 in FIG. 2D is designed as a spring ring with a trapezoidal cross-section.

In Fig. 3, the configuration of the fixing element 29 is shown as a clamping sleeve. The clamping sleeve can be made of solid material and executed inelastic in contrast to the spring elements described above. In this case, the clamping sleeve is pressed in in FIG. 3A and welded to the magnet sleeve 15 in FIG. 3B. In this case, at least in the exemplary embodiment in FIG. 3B, a geometrical clamping feature 37 on the magnet sleeve 15 can be dispensed with.

4, an embodiment of the fixing element 29 is shown as a spiral spring. Similar to the spring element and to the clamping sleeve, the spiral spring can extend in a plane perpendicular to the longitudinal axis 35 of the magnet assembly 3 in a ring-shaped or segment-like manner around the armature 17. In this case, the coil spring is biased in the axial direction and can be supported for example on the dial 23 or on the magnet sleeve 15. In Fig. 5 different configurations are shown with different cross sections of the fixing element 29 as a spring element. In this case, the fixing element 29, each engage with a receiving element in the magnet sleeve 15 of the magnet assembly 3. This is not shown in the figures. In Fig. 5A, the fixing element is designed as a cross-sectionally S-shaped spring element. The lower region of the spring element is optionally supported on an adjacent component. In Fig. 5B, the fixing element 29 is wavy in a cross-section parallel to the longitudinal axis 35 executed. In FIG. 5C, the fixing element 29 is designed as a bent spring element which is elongated in a cross section parallel to the longitudinal axis 35 and which is designed similarly to the embodiment in FIG. 5A.

In conclusion, it should be noted that terms such as "comprising" or the like are not intended to exclude that other elements or steps may be envisioned.Furthermore, it should be understood that "a" or "an" does not exclude a multitude Embodiments described features are combined with each other as desired.

It is further noted that the reference signs in the claims should not be construed as limiting the scope of the claims.

Claims

claims

Magnetic assembly (3) for a fuel! Njektor (1), the magnet assembly (3) having

an electromagnet (5) having a magnetic core (7) and a magnetic coil

(9);

an armature (17) which is movable by means of the electromagnet (5) in the direction of a longitudinal axis (35);

a residual air gap disc (25) for adjusting a distance between the magnetic core (7) and the armature (17);

wherein the residual air gap disc (25) is disposed between the magnetic core (7) and the armature (17);

characterized in that

the residual air gap disc (25) is fixed in a direction parallel to the longitudinal axis (35) of the magnet assembly (3) by a fixing member (29), the fixing member (29) being separate from the residual air gap disc (25).

Magnetic assembly (3) according to claim 1,

wherein the fixing element (29) fixes the residual air gap disk (25) in such a way that a rotationally symmetrical introduction of force into the residual air gap disk (25) takes place relative to the longitudinal axis (35).

Magnetic assembly (3) according to one of claims 1 and 2,

wherein the fixing member (29) fixes the residual air gap disc (25) in a direction perpendicular to the longitudinal axis (35) of the magnet assembly (3).

Magnetic assembly (3) according to one of claims 1 to 3,

wherein the fixing element (29) is designed as a parallel to the longitudinal axis (35) of the magnet assembly (3) biased spring element. Magnetic assembly (3) according to claim 4,

wherein the fixing element (29) is designed as a spring ring;

wherein the spring ring has an oval, a circular, a trapezoidal or a C-shaped cross-section.

Magnetic assembly (3) according to claim 4,

wherein the fixing element (29) is designed as a spiral spring or as a wave spring.

Magnetic assembly (3) according to one of claims 1 to 3, wherein the fixing element (29) is designed as a clamping sleeve.

Magnet assembly (3) according to one of claims 1 to 7, wherein the fixing element (29) between the residual air gap disc (25) and the armature (17) is clamped, pressed and / or welded.

Magnet assembly (3) according to one of claims 1 to 8, wherein the electromagnet (5) is arranged in a magnet sleeve (15);

wherein the magnet sleeve (15) comprises a clamping element (37), which is designed, the fixing element (29) in a direction parallel to the longitudinal axis (35) of the

Press magnet assembly (3) against the residual air gap disc (25);

and or

wherein the magnet sleeve (15) has a receiving member adapted to receive an end portion of the fixing member (29) and to prevent it from slipping in a direction perpendicular to the longitudinal axis (35) of the magnet assembly (3).

10. Magnet assembly (3) according to one of claims 1 to 9,

the electromagnet (5) having an inner pole (11) and an outer pole (13) o;

wherein the residual air gap disc (25) is fixed in the region of the outer pole (23).