Modular actuator unit for a fuel injection valve

Abstract

An actuator unit for a fuel injection valve of a vehicle internal combustion engine. The actuator unit includes an electronic component formed as a stack. The component includes a plurality of electrode layers and a plurality of material layers which are arranged alternately and react to the application of an electric field. The component also has two outer electrodes electrically connected to respective electrode layers on at least one circumferential side of the component. Additionally, the actuator unit has a piezoelectric sensor coupled to the component in a force-fitting manner, in the stroke direction of the component. When the component is in operation, the sensor detects a force generated by the component, as a voltage or charge between two electrodes arranged on opposing end faces, of a sensor element. The electrodes are deposited from an electrically conductive material directly onto at least the end faces of the sensor element.

Claims

1. An actuator unit for an injection valve of an internal combustion engine of a vehicle, comprising: an electronic component in the form of a stack, with a plurality of inner stack electrode layers; a plurality of layers of material that react to the application of an electric field, wherein layers of material and the inner stack electrode layers are stacked alternately; and two outer stack electrodes, to which the inner stack electrode layers are each alternately electrically connected on at least one peripheral side of the component; a piezoelectric sensor comprising a sensor body and two outer sensor electrodes disposed on opposite end faces of the sensor body, wherein one of the two outer sensor electrodes of the piezoelectric sensor is coupled to the component through an insulation layer in a force-fit manner in the stroke direction of the component, and the piezoelectric sensor detects a force generated and applied to the one of the two outer sensor electrodes by movement of the component during operation of the component, the force applied to the one of the two outer sensor electrodes being detected as a voltage or charge between the two outer sensor electrodes, wherein the two outer sensor electrodes are comprised of electrically conductive material deposited directly onto at least one of the end faces of the sensor body.

2. The actuator unit as claimed in claim 1, in which a respective end face of the sensor body is bounded by side edges, wherein the electrode disposed on the respective end face is spaced apart from at least one of the associated side edges by a spacing.

3. The actuator unit as claimed in claim 1, in which the electrodes are produced by plasma deposition or sputtering or vapor deposition.

4. The actuator unit as claimed in claim 1, in which the sensor is connected to the component in a force-fit manner by an insulation layer.

5. The actuator unit as claimed in claim 1, in which at least one contacting segment of a respective electrode is disposed on at least one lateral surface of the sensor body, wherein the at least one contacting segment and the associated electrode are produced over a side edge in one step.

6. The actuator unit as claimed in claim 5, in which at least on a side edge opposite the contacting segment the spacing is provided between the electrode and said side edge.

7. The actuator unit as claimed in claim 1, in which the sensor body is a monolithic plate made of a piezo ceramic.

8. The actuator unit as claimed in claim 7, in which the piezo ceramic of the sensor is made of a different material from the layers of material of the component.

9. The actuator unit as claimed in claim 1, in which the electrodes have a layer thickness of less than 20 m.

10. The actuator unit as claimed in 2, in which the electrodes have a layer thickness of less than 10 m.

11. The actuator unit as claimed in claim 9, in which a respective end face of the sensor body is bounded by side edges, wherein the electrode disposed on the respective end face is spaced apart from at least one of the associated side edges by a spacing.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) Aspects of the invention are explained in detail below using exemplary embodiments in the figures. In the figures:

(2) FIG. 1 shows a schematic representation of an actuator unit according to the invention,

(3) FIG. 2 shows a first exemplary embodiment of a sensor configured according to the invention for the actuator unit according to FIG. 1,

(4) FIG. 3 shows a second exemplary embodiment of a sensor configured according to the invention for the actuator unit according to FIG. 1,

(5) FIG. 4 shows a third exemplary embodiment of a sensor configured according to the invention for the actuator unit according to FIG. 1, and

(6) FIG. 5 shows a fourth exemplary embodiment of a sensor configured according to the invention for the actuator unit according to FIG. 1.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

(7) FIG. 1 shows in a schematic representation an actuator unit according to an aspect of the invention for an injection valve of an internal combustion engine of a vehicle. The same comprises an electronic component 10 in the form of a stack. Such a stack 16 usually has a rectangular or square cross-section when seen in plan view. The component stack 16 comprises (not visible in FIG. 1) a plurality of electrode layers or a plurality of layers of material that react to the application of an electric field, wherein each of the layers of material is disposed 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 by means of schematically represented conductors 13, 14. The outer electrodes 11, 12 are connected to a control unit 17 (ECU-Electronic Control Unit) for activating the component stack 16. The outer electrodes 11, 12 are disposed on at least one peripheral side, but preferably on two different peripheral sides of the stack, which are in particular preferably opposite each other.

(8) 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 piezoelectric actuator) can be achieved.

(9) In order to be able to mechanically protect the component stack provided with the two outer electrodes, an insulation layer, for example of silicon (not shown), is usually applied to the peripheral sides of the component stack. In order to be able to prevent damage to the component stack during its actuation by an actuator and otherwise to be able to exert a restoring force on the component stack if activation by means of the two outer electrodes 11, 12 is no longer occurring, a tubular spring enclosing the component 10 (not shown) is provided. The tubular spring is typically made of a metal. Whereas the lower end of the component stack 16 in the plate direction is brought into engagement with a needle (also not shown) of an injection valve or a different component of a hydraulic system of the injection valve, in order to inject fuel into a combustion chamber in the event of deflection of the component stack 16, a sensor 20 is connected to the component stack 16 on the upper end in the plate direction in a force-fit manner in the stroke direction of the component stack 16. The sensor 20 can for example be supported on a housing component (not shown) of the injection valve for this purpose.

(10) The sensor 20 comprises a sensor body 21, which is formed by a monolithic plate of a piezo ceramic. During operation of the component 10 the sensor 20 detects a force F produced by the component stack 16, which can be detected as a voltage between two electrodes 24, 25 disposed on opposite lateral surfaces 22, 23 of the sensor body 21. The electrodes 24, 25 are connected to a voltage measurement device 30 for this purpose, which detects the voltage produced by the piezo ceramic and converts the same into the force correlated therewith.

(11) An insulation layer 31, 32 is applied to each of the electrodes 24, 25 in order to prevent an electrical short circuit of the so-called outer electrode 24 to the housing of the injection valve or of the so-called inner electrode 25 to the component 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 lateral surface 26a, 26b, 26c, 26d of the sensor body by means of contacting segments 27a, 27b, 27c, 27d of the electrodes 24, 25.

(12) The thickness of the sensor body 21 is approximately 0.5 mm. The lengths of the side edges are for example between 2 and 3 mm, wherein other dimensions are also possible. Typically, the side lengths of the sensor body are chosen to equal the side lengths of the actuator. The sensor body 21 can optionally have a square, a rectangular or a different cross-section in plan view. The electrodes 24, 25 are applied from an electrically conductive material directly on at least the end faces of the sensor body. Directly means that the electrode material is applied directly onto the sensor body by the manner of the generation of the contact without an adhesive or other adhesive material. For example silver, gold or copper, palladium or alloys thereof can be used as electrically conductive material. Said materials can be applied directly onto 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 a plurality of contacting segments 27a, 27b, 27c, 27d can also be applied to one or a plurality of lateral surfaces 26a, 26b, 26c, 26d of the sensor body 21, for example by turning of the sensor body 21 during manufacture. By using masking during the manufacturing process, any contours of the electrodes 24, 25 and/or of the contacting segments 27a, 27b, 27c, 27d can be produced during this.

(13) Said methods for the direct application of the material of the electrodes 24, 25 enable, in comparison with metal films, very thin electrodes of about 10 to 20 m thickness. At the same time, a very flat surface can be achieved, so that a stiff connection to the component stack is possible.

(14) FIGS. 2 to 5 each show in a perspective representation different exemplary embodiments of a sensor 20 that is used in an actuator unit according to FIG. 1. The exemplary embodiments differ in the shape of the electrodes and the arrangement or number of the contacting segments. Because of the perspective representation, in each case only the outer electrode 24 on the end face 22 and the side edges 26c and 26d of the sensor body with the contacting segment(s) 27c, 27d can be seen.

(15) In FIG. 2 the electrode 24 extends over the entire surface of the end face 22. The result of this is that the electrode extends to the four side edges 22a, 22b, 22c, 22d the end face 22. A contacting segment 27c is disposed on the lateral surface 26c.

(16) In FIG. 3 the electrode 24 is spaced apart from each of the side edges 22a, 22b, 22c, 22d by a spacing 28a, 28b, 28c, 28d. The contacting segment 27c is again disposed on the side edge 26c. The spacing enables the omission of further lateral insulation measures.

(17) In FIG. 4 the electrode 24 is spaced apart only from the side edge 22a by a spacing 28a. Otherwise the electrode extends to the side edges 22b, 22c, 22d. The contacting segment 27c is again disposed on the side edge 26c. Similarly, the electrode 25 is spaced apart from the side edge 23c, wherein the contacting segment is disposed on the non-visible lateral surface 26a, i.e. opposite the contacting segment 27c. Said embodiment also enables the omission of otherwise usual insulation measures.

(18) In FIG. 5 the electrode 24 is spaced apart from the side edges 22a and 22b by a spacing 28a, 28b. Otherwise the electrode extends to the side edges 22c, 22d. The contacting segment 27c is again disposed on the lateral surface 26c. In addition, a contacting segment 27d is provided on the lateral surface 26d. Similarly, the electrode 25 is spaced apart from the side edges 23c, 23d, wherein the contacting segments are disposed on the non-visible end faces 26a and 26b, i.e. opposite the contacting segments 27c, 27d. Said embodiment enables the omission of otherwise usual insulation measures and enables low-resistance contacting of the electrodes 24, 25.

(19) In the exemplary embodiments described, the contacting segments and the associated electrode are produced in one step and form a unit. The represented contacting segment(s) only occupy, only by way of example, a part of the surface of the relevant side edge. For example, the contacting segment 27c could also extend to the side edge 23c of the end face 23. Likewise, the contacting segment 27c could also occupy a greater width. It could even extend over the entire lateral surface 26c. The same applies to the contacting segment 27d in FIG. 5 or all contacting segments provided on the sensor body 21.

(20) By the direct application of the electrodes to the sensor body, the elasticity of the coupling region between the sensor and the component stack can be reduced or even almost completely eliminated. In particular, there is no loss of stiffness as a result of the conventionally used adhesive. The omission of adhesive has the further advantage that no contamination can occur as a result of solvent-adhesives.

(21) The proposed embodiment enables the separate manufacture of the sensor and the piezoelectric actuator, which can be joined together at a later point in time.