EP2948672A1

EP2948672A1 - Modular actuator unit for a fuel injection valve

Info

Publication number: EP2948672A1
Application number: EP14721245.0A
Authority: EP
Inventors: Claus Zumstrull
Original assignee: Continental Automotive GmbH
Current assignee: Continental Automotive GmbH
Priority date: 2013-04-17
Filing date: 2014-04-16
Publication date: 2015-12-02
Also published as: US9709186B2; WO2014170399A1; US20160053910A1; DE102013206933A1

Abstract

The invention relates to an actuator unit for a fuel injection valve of an internal combustion engine of a vehicle. The actuator unit comprises an electronic component (10) formed as a stack. Said component (10) comprises a plurality of electrode layers and a plurality of material layers which react to the application of an electric field, the material and electrode layers being arranged alternately. The component (10) also comprises two outer electrodes (11, 12) which are electrically connected to respective electrode layers on at least one circumferential side of the component (10). In addition, the actuator unit comprises a piezoelectric sensor (20) that is coupled to the component (10) in a force-fitting manner, in the stroke direction of the component (10). When the component (10) is in operation, the sensor (20) detects a force (F) generated by the component, which can be detected as a voltage or charge between two electrodes (24, 25) arranged on opposing end faces (22, 23) of a sensor element (21). The electrodes (24, 25) are deposited from an electrically conductive material directly onto at least the end faces (22, 23) of said sensor element (21).

Description

description

Modular actuator for an injection valve, the invention relates to a modular actuator for an injection valve of an internal combustion engine of a driving ^¬ zeugs. Such an actuator unit is used for injecting fuels into a combustion chamber of a cylinder of the internal combustion engine.

An actuator for an injection valve of a Burn ^¬ voltage combustion engine of a vehicle typically includes a formed as a stacking device having a plurality of electrode layers and a plurality of responsive to applying an electric field layers of material, each material layer between two disposed electrode layers ^¬ the. Such a component of überei ^¬ Nander and alternately to each other stacked layers of material layer and electrode layer is generally referred to as a stack. The nowadays most well-known electronic component of this kind is generally referred to as a piezoelectric actuator stack, which is used as an actuating element in injection valves of the various ^¬ most engine types for motor vehicles. The material layers are ceramic layers in this piezoelectric actuator.

Usually, such a stack, viewed in plan view, has a rectangular or square cross-section. The stack is typically electrically contacted at two opposite circumferential sides. To be able to carry this out technologically carefully, the electrode layers are geometrically designed, for example, such that only every second electrode layer extends laterally to one of the two circumferential sides, while the respective other electrode layers do not extend to this one circumferential side. The same applies analogously to the other circumferential side of the stack. The electrical contacting of the electrode layers takes place via two outer electrodes, which are generally electrically connected to respective electrode layers on at least one peripheral side of the component and typically on two opposite circumferential sides.

The finished component is surrounded by a Bourdon tube, which is typically made of a metal. The tube spring serves to bias the component stack during operation of the actuator unit and thereby prevent damage to the ceramic. Furthermore, the tube spring serves to provide a restoring force for the deflected component stack. As an insulating material between the Bourdon tube and the outer electrodes of the component stack, a layer, e.g. made of silicone, which covers at least the outer electrodes.

With increasing demands on emissions and consumption, the requirements for injection of the fuel into the combustion chamber increase. Higher pressures, temperatures and Mehrfacheinsprit tongues therefore require a higher accuracy in the metering of the injected fuel. In order to achieve the required accuracies, it is therefore not sufficient to operate the actuator in a control mode. Rather, a regulation is needed. For the control, defined measured variables are required, which are determined on or in the actuator unit in order to calculate the corresponding control variables therefrom.

For this example, sensors can be used, which directly detect the opening and closing time of a actuated by the actuator needle of the injection valve. Such a sensor may be, for example, a piezoelectric force sensor, which is coupled in the frictional connection with the piezoelectric actuator. However, while recoverable Messge ^¬ accuracy is not high enough for precise control.

It is therefore an object of the present invention to provide an actuator unit for an injection valve of an internal combustion engine of a vehicle, which structurally and / or functionally is improved, so that a higher measurement accuracy of the force curve of the piezoelectric actuator is achieved.

This object is achieved by an actuator unit according to the features of claim 1. Advantageous embodiments emerge from the dependent claims.

The invention provides an actuator unit for an injection valve of an internal combustion engine of a vehicle. The actuator unit comprises a designed as a stack elekt ^¬ ronic component. The component has a plurality of electrode layers and a plurality of material layers reacting upon application of an electric field, wherein the material layers and electrode layers are each stacked in an alternating manner. The component further comprises two outer electrodes, with which the electrode layers are alternately electrically connected to at least one circumferential side of the component. Furthermore, the actuator unit comprises a piezoelectric sensor which is non-positively coupled with the component in the stroke direction of the component. In operation of the device, the sensor detects a force generated by the construction ^¬ element, which is detected as a voltage or charge between two arranged on opposite end faces of a sensor body electrodes. The electrodes are applied from an electrically conductive material directly to at least the end faces of the sensor body.

The invention is based on the finding that the coupling point between the component (piezoactuator) and the sensor with regard to its rigidity and force transmission is of great importance for high measuring accuracy. In conventional piezoelectric sensors, the electrodes are formed by, on the side and end faces applied, metal foils, which are connected via an adhesive to the side and end faces of the sensor body. Since the metal foils can not be applied completely flat to the sensor body and the adhesive has elastic properties even after curing, the result is an overall elastic coupling region. which distorts the measurement of the force generated by the component or does not reflect the time course correctly.

By the present invention direct application of the electrodes on the sensor body, for example, by plasma deposition or evaporation or sputtering, can be the elasticity of the coupling region ^¬ re duce or even almost completely eliminated. In particular, there is no loss of stiffness due to the conventionally used adhesive. Abandoning adhesive has the further advantage that no contamination can occur by Lösemit ^¬ tel adhesives.

The end faces represent opposing main sides of the sensor body, which are arranged parallel to each other. The main sides of the sensor body are preferably arranged in the actuator unit parallel to the material layers or the electrode layers of the component (piezoelectric actuator).

The electrodes applied directly to the sensor body can have a different thickness. You can also have the same thickness.

The geometry of the two electrodes is freely selectable. The geometry may e.g. be determined by a mask or the like.

The proposed embodiment allows a separate Fer tion of sensor and piezoelectric actuator, which can be joined together at a later date.

The material used for the electrodes may be metals such as silver, copper, gold, palladium or alloys thereof. Other conductive materials are possible. The higher rigidity of the coupling region is further favored in that the direct application of the electrodes enables a lower electrode thickness. While in a conventional actuator unit ^¬ forth the thickness of the metal foil between _n

5

50μ and 80μm, the thickness of the electrodes can be reduced to less than 20 μm, in particular less than 10 μm, according to one embodiment. According to another embodiment a respective end face is limited by side edges, which is arranged on the respective end surface electrode includes at least one of the parent to ^¬ side edges a distance. As a result, an unwanted electrical connection to the outer electrodes of the piezoelectric actuator or other conductive components can be avoided without further measures.

According to a further expedient embodiment, at least one contacting section of a respective electrode is arranged on at least one side surface of the sensor body, wherein the at least one contacting section and the associated electrode are generated over a side edge in one step. The contacting portions on the side surface are used for the electrical contacting of the electrodes. The fact that these - in contrast to conventional Aktuator- units - are now arranged on the side surfaces, simplifies the overall structure of the actuator unit.

In conventional sensor units in which the electrodes are formed by metal foils, they can not be bent over to the side surface due to the small thickness of the sensor body (usually less than 0.5 mm). Instead, the contacting section of the electrode facing the stack (so-called internal electrode) in the direction of the piezoelectric actuator and the electrode facing away from the stack (so-called external electrode) must be bent in the direction of an insulator. In particular for the inner ^¬ electrode suitable isolation measures must be taken for this, which is not necessary in the inventive procedure.

According to a further expedient embodiment, the distance between the electrode and this side edge is at least on a Bei ^¬ tenkante opposite the contacting section intended. This avoids isolation problems with respect to the outer electrodes of the piezoelectric actuator without separate further measures. According to a further expedient embodiment, the sensor body is a monolithic plate made of a piezoceramic. In particular, the piezoceramic of the sensor may be formed of a different material than the material layers of the component.

According to a further expedient embodiment, the sensor is non-positively connected to the component via an insulating layer. Likewise, the sensor can be supported on the side facing away from the piezoelectric actuator side via an insulating layer on a housing of the actuator unit.

The invention will be explained in more detail below with reference to embodiments ^¬ examples in the drawing. 1 shows a schematic representation of a device according to the invention

actuator,

2 shows a first exemplary embodiment of a sensor designed according to the invention for the actuator unit according to FIG. 1, FIG.

FIG. 3 shows a second exemplary embodiment of a sensor designed according to the invention for the actuator unit according to FIG. 1, FIG.

4 shows a third exemplary embodiment of a sensor designed according to the invention for the actuator unit according to FIG. 1, and FIG. 5 shows a fourth exemplary embodiment of a sensor configured according to the invention for the actuator unit according to FIG. 1. 1 shows a schematic illustration of an actuator unit according to the invention for an injection valve of an internal combustion engine of a vehicle. This comprises an electronic component 10 designed as a stack. Such a stack 16, as viewed in plan view, usually has a rectangular or square cross section. The component stack 16 comprises (not visible in FIG. 1) a plurality of electrode layers or a plurality of material layers responsive to application of an electric field, wherein each of the material layers is arranged between two of the electrode layers. The electrical contacting takes place via two outer electrodes 11, 12, which are electrically connected to respective electrode layers via schematically represented conductors 13, 14. The outer electrodes 11, 12 are connected to drive the component stack 16 with a control unit 17 (ECU Electronic Control Unit). The outer electrodes 11, 12 are arranged at least on one peripheral side, but preferably on two different circumferential sides of the stack, which are particularly preferably opposite.

By applying an electric field to the two outer electrodes 11, 12 by means of a control signal of the control unit 17, a deflection of the component stack 16 (so-called.

Piezo actuator) can be achieved.

In order to be able to mechanically protect the component stack provided with the two outer electrodes, an insulating layer, for example of silicone, is usually applied to the peripheral sides of the component stack (not shown). In order to prevent damage to the component stack during its aktuatorischer operation and on the other hand to be able to exert a restoring force on the component stack when a driving across the two outer electrodes 11, 12 no longer takes place, is a (not shown) measures the component 10 surrounding tube spring ^¬ see. The Bourdon tube is typically ge ^¬ made of a metal. While the lower sheet-direction end of the component stack is contacted with a, also not shown needle of an injection valve or other component of a hydrau ^¬ metallic system of the injection valve in engagement 16 to inject 16 fuel at a deflection of the component stack into a combustion chamber, is at the upper end in the sheet direction, a sensor 20 in the stroke direction of the component stack 16 frictionally connected to the component stack 16. For this purpose, the sensor 20 can be supported, for example, on a housing component, not shown, of the injection valve.

The sensor 20 comprises a sensor body 21, which is formed by a monolithic plate made of a piezoceramic. During operation of the component 10, the sensor 20 detects a force F generated by the component stack 16, which can be detected as a voltage between two electrodes 24, 25 arranged on opposite side surfaces 22, 23 of the sensor body 21. For this purpose, the electrodes 24, 25 are connected to a voltage measuring device 30, which detects the voltage generated by the piezoceramic and converts it into the force correlating thereto.

To the electrodes 24, 25 is a respective insulation layer 31, applied 32 to prevent an electrical short of the so-called. External electrode 24 to the housing of the injection valve or the so-called. Inner electrode 25 to the device stack 16 or its outer ^¬ electrodes 11,12. For this reason, the contacting of the electrodes 24, 25 does not take place in the region of the end faces 22, 23, but in the region of a side face 26a, 26b, 26c, 26d of the sensor body via contacting sections 27a, 27b, 27c, 27d of the electrodes 24, 25.

The thickness of the sensor body 21 is about 0.5 mm. The lengths of the side edges are for example between 2 and 3 mm, although other dimensions are possible. Typically, the side lengths of the sensor body are chosen equal to the side lengths of the actuator. The sensor body 21 can optionally have a square, a rectangular or another cross-section in plan view. The electrodes 24, 25 are applied from an electrically conductive material directly at least on the end faces of the sensor body. Direct means that the electrode material is applied without adhesive or other adhesive material directly by the way the generation of the contact on the sensor body. As the electrically conductive material, for example, silver, gold or copper, palladium or alloys thereof may be used. These materials can be applied directly to the sensor body 21 by plasma deposition, vapor deposition or sputtering. Together with the electrodes 24, 25 applied to a respective end face 22, 23, one or more contacting sections 27a, 27b, 27c, 27d can also be applied to one or more side faces 26a, 26b, 26c, 26d of the sensor body 21, for example by rotation of the Sensor body 21 during manufacture. By masking during the manufacturing process, any desired contours of the electrodes 24, 25 and / or the contacting sections 27a, 27b, 27c, 27d can be generated. The mentioned methods for direct application of the material of the electrodes 24, 25 allow compared to metal foils very thin electrodes of about 10 to 20 ym thickness. At the same time, a very even surface can be achieved, so that a rigid connection to the component stack is possible.

FIGS. 2 to 5 each show, in a perspective view, various embodiments of a sensor 20 which is used in an actuator unit according to FIG. The embodiments differ in the shape of the electrodes and the arrangement or number of contacting portions. Due to the perspective view, only the outer electrode 24 on the end face 22 and the side edges 26c and 26d of the sensor body with the contacting section (s) 27c, 27d are visible.

In Fig. 2, the electrode 24 extends over the entire surface of the end face 22. This has the consequence that the electrode up to the four side edges 22a, 22b, 22c, 22d of the end face 22nd protrudes. A contacting portion 27c is disposed on the side surface 26c.

In Fig. 3, the electrode 24 at each of the side edges 22a, 22b, 22c, 22d at a distance 28a, 28b, 28c, 28d. The con ^¬ taktierungsabschnitt 27c is again arranged on the side edge 26c. The distance makes it possible to dispense with further, lateral isolation measures. In Fig. 4, the electrode 24 only at the side edge 22a at a distance 28a. Otherwise, the electrode extends right up to the sides ^¬ edges 22b, 22c, 22d. The contacting portion 27c is again disposed on the side edge 26c. In a corresponding manner, the electrode 25 is at a distance from the side edge 23c, wherein the contacting portion is disposed on the non-visible side surface 26a, ie opposite the contacting portion 27c. This refinement likewise makes it possible to dispense with otherwise customary isolation measures. In Fig. 5, the electrode 24 to the side edges 22a and 22b at a distance 28a, 28b. Otherwise, the electrode projects up to the side edges 22c, 22d. The contacting portion 27c is again disposed on the side surface 26c. In addition, a contacting portion 27d is provided on the side surface 26d. In a corresponding manner, the electrode 25 is at a distance from the side edges 23c, 23d, wherein the Kontak- tierungsabschnitte on the non-visible end faces 26a and 26b, that are arranged opposite the contacting sections 27c, 27d. This refinement makes it possible to dispense with otherwise customary insulation measures and a lower resistance contacting of the electrodes 24, 25.

In the exemplary embodiments described, the contact portions and the associated electrode are produced in one step and form a unit. The or Darge ^¬ presented contacting sections take only an example of a part of the surface of the respective side edge. For example, the contacting portion 27c could also be up to the side edge 23c of Face 23 protrude. Likewise, the contacting portion 27c could also occupy a greater width. It could also extend over the entire side surface 26c. The same applies to the contacting section 27d in FIG. 5 or all contacting sections provided on the sensor body 21.

By directly applying the electrodes to the sensor body, the elasticity of the coupling region between the sensor and the component stack can be reduced or even eliminated almost completely. In particular, there is no loss of stiffness due to the conventionally used adhesive. The absence of adhesive has the further advantage that no contamination by solvent adhesives can occur. The proposed configuration allows separate Ferti ^¬ supply of the sensor and the piezoelectric actuator, which can be joined at a later date.

Claims

claims

Actuator for an injection valve of a Burn ^¬ voltage combustion engine of a vehicle, comprising:

a trained as a stack electronic component

(10), with

a plurality of electrode layers;

a plurality of material layers responsive to application of an electric field, wherein material layers and electrode layers are each stacked alternately; and

two outer electrodes, with which the electrode layers are alternately electrically connected on at least one circumferential side of the ^{component ¬} (10);

a piezoelectric sensor (20) comprising a sensor body (21) and two electrodes (24, 25) arranged on opposite end faces (22, 23) of the sensor body (21),

wherein the piezoelectric sensor (20) in the lifting direction of the component (10) is non-positively coupled to the component (10) and detects during operation of the component (10) a force generated by the component (10), which as a voltage or charge between the electrodes (24, 25) is detectable,

wherein the electrodes (24, 25) made of an electrically conductive material are applied directly to at least the end faces (22, 23) of the sensor body (21).

Actuator unit according to Claim 1, in which the electrodes (24, 25) have a layer thickness of less than 20 μm and in particular less than 10 μm.

Actuator unit according to Claim 1 or 2, in which a respective end face (22, 23) of the sensor body is delimited by side edges (22a, 22b, 22c, 22d; 23a, 23b, 23c, 23d), which are fixed on the respective end face (22, 23). 23) arranged electrode (24, 25) at least to one of the associated Side edges (22a, 22b, 22c, 22d, 23a, 23b, 23c, 23d) has a distance (28a, 28b, 28c, 28d).

Actuator unit according to one of the preceding claims, in which at least one contacting section (27a, 27b, 27c, 27d) of a respective electrode (24, 25) is arranged on at least one side face (26a, 26b, 26c, 26d) of the sensor body (21), wherein the at least one contacting ^¬ section and the associated electrode (24, 25) via a side edge (22a, 22b, 22c, 22d, 23a, 23b, 23c, 23d)) are generated in one step away.

Actuator unit according to Claims 3 and 4, in which the spacing (28a, 28b, 28c, 28d) between the electrode (24, 25) and this side edge (22a, 22b) at least at one side opposite the contacting portion (27a, 27b, 27c, 27d). 22b, 22c, 22d; 23a, 23b, 23c, 23d).

Actuator unit according to one of the preceding claims, wherein the sensor body (21) is a monolithic plate made of a piezoceramic.

7. Actuator unit according to claim 6, wherein the piezoceramic of the sensor (20) is formed of a different material than the material layers of the component.

8. Actuator unit according to one of the preceding claims, wherein the electrodes (24, 25) are generated by a plasma deposition or sputtering or vapor deposition.

9. Actuator unit according to one of the preceding claims, wherein the sensor (20) via an insulating layer with the component (10) is non-positively connected.