DE102013212504A1 - Magnetic assembly for a fuel injector - Google Patents

Abstract

A magnet assembly (3) for a fuel injector (1) is presented. The magnet assembly (3) has an electromagnet (5) with a magnet core (7) and a magnet coil (9). The magnet assembly (3) also has an armature (17) for moving a valve member and a residual air gap disc (25) for setting a distance between the magnet core (7) and the armature (17). The remaining air gap disc (25) is arranged between the electromagnet (5) and the armature (17). Furthermore, the remaining 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 separately from the residual air gap disc (25).

Description

State of the art

A fuel injector for motor vehicles may have a solenoid valve for controlling a fuel pressure in the fuel 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.

During operation of the fuel injector, the armature stroke, that is to say the tightening and releasing of the armature, in connection with displacement and filling of the gap between armature and magnetic core with medium, results in a more or less pronounced or changing hydraulic adhesion or adhesion of the residual air gap disc Anchor or on the magnetic core. As a result, different closing conditions and thus also different closing durations of the armature in injector operation can arise.

These closing duration influences can in turn cause duration variations of the injection duration and thus also variations in the injection quantity of the fuel injector. Especially with small injection quantities for a pilot injection, such scattering may be undesirable.

Out EP 2 254 130 A2 is a Restluftspaltscheibe known which has projections and is fixed on these projections in position. 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 injector for a magnet assembly which, in particular, enables 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 injector is 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 enables reliable operation of the fuel injector.

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 also undesirably take into account the variations in the closing duration caused by hydraulic adhesion of the residual air gap disk in known magnet assemblies. In the embodiment of the magnet assembly according to the invention with the fixing element such "temporary" corrections can be avoided by the control unit. In this case, the control unit only corrects wear-related closing duration drifts.

Another advantage of the embodiment of the magnet assembly according to the invention can be seen in the fact that no structural changes are necessary on the fuel injector or on the magnet assembly. 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 used to control a fuel pressure in a control chamber of an injector, 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 member fixes the residual air gap disc in a direction parallel to a longitudinal axis, that is, in the axial direction of the magnet assembly and the fuel injector, respectively. The axial direction corresponds to the direction of movement of the valve piston of the fuel injector.

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 magnet sleeve, such as annular grooves or bevels in the axial direction. In one embodiment, as an axially resilient spring ring, the defined stiffness of the spring ring may optionally exert a desired axial force on the residual air gap disk in combination with a fitting-related compression of the spring ring.

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 loading or pretensioning of the fixing element runs along the spring axis, which coincides with the longitudinal axis of the magnet assembly.

According to a further embodiment of the invention, the fixing element is designed as a clamping sleeve. A clamping sleeve may be a solid material element, which is pressed or clamped between the residual air gap disc and the anchor plate, for example by 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 member adapted to press the fixing member against the residual air gap disc in a direction parallel to the longitudinal axis of the magnet assembly; 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.

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

2 shows different embodiments of the fixing as a spring ring

3 shows different embodiments of the fixing as a clamping sleeve

4 shows an embodiment of the fixing element as a spiral spring

5 shows further embodiments of the fixing element with different cross sections

All 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 relations are not shown to scale in the figures. In the various figures, corresponding elements are provided with the same reference numbers.

In 1 is a cross section through a magnet assembly 3 shown. The magnet assembly 3 is doing a part of a fuel injector 1 dar. The magnet assembly 3 can be used as a solenoid valve to control a fuel pressure in the fuel injector 1 or be executed 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 magnet assembly 3 has an electromagnet 5 and a movable anchor 17 on. The electromagnet 5 is in a magnet sleeve 15 arranged and has a magnetic coil 9 and a magnetic core 7 on. The anchor 17 has an anchor plate 19 and an anchor bolt 21 on. Between the anchor plate 19 and the magnetic core 7 is a residual air gap disk 25 provided, which has a residual air gap 27 between the electromagnet 5 and the anchor 17 determines and contributes to the damping of the anchor movement. The electromagnet 5 has a Magnetkerninnenpol 11 and a magnetic core outer pole 13 on. The magnetic core inner pole 11 is closer to a longitudinal axis 35 arranged as the magnetic core outer pole 13 , The residual air gap disk 25 is in the area of the magnetic core outer pole 13 arranged and can therefore as an external residual air gap 25 be designated.

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 may cause variations in the injection amount of the fuel injector. 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. Further, wear of the projections reduces the life of the residual air gap disc.

In the embodiment of the magnet assembly according to the invention 3 is between the residual air gap disk 25 and the anchor plate 19 or one with the magnet sleeve 15 connected shim 23 an additional separately executed fixing 29 made of non-magnetic material. The fixing element 29 fixes the residual air gap disc 25 in the axial direction, that is in a direction parallel to the longitudinal axis 35 the magnet assembly 3 , As a result, a stable or constant state between the anchor 17 and the residual air gap disk 25 produced. In other words, mixed states of the residual air gap disk become 25 between hydraulic bonding and detachment thanks to the fixing element 29 avoid.

In addition to the axial fixation, the residual air gap disc 25 through the fixing element 29 radially centered. Furthermore, the fixing element 29 so executed and on the magnet assembly 3 arranged that a flow of a flow and return flow in the direction of return 33 (in 1 up) is guaranteed. That is, the control or return amount, as in previous magnet assemblies in the center of the magnetic core 7 along the valve spring 31 and also between the magnet sleeve 15 and the outer periphery of the magnetic core 7 run off without the fixing element 29 to be disabled.

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

In 2A is the fixing element 29 designed as a spring ring with oval cross-section. It is in the magnet sleeve 15 a designed as an annular groove clamping element 37 intended. The spring ring is arranged in such a way in the annular groove, that he the residual air gap disc 25 in the axial direction against the Magnetkernaußenpol 13 suppressed. In 2 B is the fixing element 29 similar to the embodiment in 2A executed. In contrast to 2A has the spring washer in 2 B a circular or circular cross-section parallel to the longitudinal axis 35 on. The spring ring is like in 2A self-locking positioned on the annular groove.

In 2C is the fixing element 29 also designed as a spring ring with a circular cross-section. In contrast to 2 B is the clamping element 37 in 2C designed as an inclined plane at an angle <90 ° with the surface of the magnetic core 7 encloses and in this way the spring washer against the residual air gap disc 25 suppressed. 2D shows one too 2C similar embodiment of the clamping feature 37 as inclined plane. Unlike the 2A to 2C is the fixing element 29 in 2D designed as a spring ring with a trapezoidal cross-section.

In 3 is the embodiment of the fixing 29 shown as a clamping sleeve. The Clamping sleeve can consist of solid material and be executed inelastic in contrast to the spring elements described above. The clamping sleeve is in 3A pressed in and in 3B with the magnet sleeve 15 welded. In this case, at least in the embodiment in 3B on a geometric clamping feature 37 at the magnet sleeve 15 be waived.

In 4 is an embodiment of the fixing 29 represented as a spiral spring. The coil spring may be similar to the spring element and the clamping sleeve in a plane perpendicular to the longitudinal axis 35 the magnet assembly 3 annular or segmental around the anchor 17 run. In this case, the coil spring is biased in the axial direction and can be, for example, on the shim 23 or at the magnet sleeve 15 support.

In 5 are different configurations with different cross sections of the fixing 29 shown as a spring element. This could be the fixing 29 , each with a receiving element in the magnet sleeve 15 the magnet assembly 3 intervention. This is not shown in the figures. In 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 5B is the fixing element 29 wave-shaped in a cross-section parallel to the longitudinal axis 35 executed. In 5C is the fixing element 29 as in a cross-section parallel to the longitudinal axis 35 elongated curved spring element carried out, which is similar to the embodiment in 5A is executed.

Finally, it should be noted that terms such as "having" or the like are not intended to exclude that other elements or steps may be provided. It should also be noted that "a" or "an" does not exclude a multitude. In addition, features described in connection with the various embodiments may be 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.

QUOTES INCLUDE IN THE DESCRIPTION

This list of the documents listed by the applicant has been generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Cited patent literature

• EP 2254130 A2 [0006]

Claims (10)

Magnetic assembly ( 3 ) for a fuel injector ( 1 ), the magnetic assembly ( 3 ) comprising an electromagnet ( 5 ) with a magnetic core ( 7 ) and a magnetic coil ( 9 ); an anchor ( 17 ), which by means of the electromagnet ( 5 ) in the direction of a longitudinal axis ( 35 ) is movable; a residual air gap disc ( 25 ) for adjusting a distance between the magnetic core ( 7 ) and the anchor ( 17 ); the residual air disc ( 25 ) between the magnetic core ( 7 ) and the anchor ( 17 ) is arranged; characterized in that the residual air gap disc ( 25 ) in a direction parallel to the longitudinal axis ( 35 ) of the magnet assembly ( 3 ) by a fixing element ( 29 ) is fixed, wherein the fixing element ( 29 ) separately from the residual air disc ( 25 ) is executed. Magnetic assembly ( 3 ) according to claim 1, wherein the fixing element ( 29 ) the residual air disc ( 25 ) is fixed such that one with respect to the longitudinal axis ( 35 ) rotationally symmetrical introduction of force into the residual air gap disk ( 25 ) takes place. Magnetic assembly ( 3 ) according to one of claims 1 and 2, wherein the fixing element ( 29 ) the residual air disc ( 25 ) in a direction perpendicular to the longitudinal axis ( 35 ) of the magnet assembly ( 3 ) fixed. Magnetic assembly ( 3 ) according to one of claims 1 to 3, wherein the fixing element ( 29 ) as parallel to the longitudinal axis ( 35 ) of the magnet assembly ( 3 ) biased spring element is executed. 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. Magnetic assembly ( 3 ) according to one of claims 1 to 7, wherein the fixing element ( 29 ) between the residual air gap disc ( 25 ) and the anchor ( 17 ) is clamped, pressed and / or welded. Magnetic assembly ( 3 ) according to one of claims 1 to 8, wherein the electromagnet ( 5 ) in a magnetic sleeve ( 15 ) is arranged; the magnetic sleeve ( 15 ) a clamping element ( 37 ), which is executed, the fixing element ( 29 ) in a direction parallel to the longitudinal axis ( 35 ) of the magnet assembly ( 3 ) against the residual air gap disc ( 25 ) to press; and / or wherein the magnetic sleeve ( 15 ) has a receiving element which is designed, an end region of the fixing element ( 29 ) and against slipping in a direction perpendicular to the longitudinal axis ( 35 ) of the magnet assembly ( 3 ). Magnetic assembly ( 3 ) according to one of claims 1 to 9, wherein the electromagnet ( 5 ) an inner pole ( 11 ) and an external pole ( 13 ) having; the residual air disc ( 25 ) in the area of the outer pole ( 23 ) is fixed.

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