DE102008055119A1 - piezoinjector - Google Patents

Abstract

A piezoinjector (12) with a piezoactuator (14) is to be designed in such a way that, when the piezoactuator (14) is blocked externally, it automatically degrades its electrical charge and this function can be realized cost-effectively in the manufacture of the piezoinjector (12). The piezoinjector (12) has leading to the piezoelectric actuator (14) leading electrical contact elements (26) which are mounted on the one hand in a connector (18) and on the other hand in a separate contact carrier (22). By making the connection plug (18) or the contact carrier (22) made of an electrically conductive plastic, an electrical path between the contact elements (26) in the function of a discrete high-impedance resistor, which allows the automatic discharge of the piezoelectric actuator (12). The piezoinjector (12) is preferably used for injecting fuel into the combustion chamber of an internal combustion engine of a motor vehicle.

Description

The The invention relates to a piezoelectric injector, preferably in the automotive sector.

State of the art

It is known per se that for the construction of a piezoelectric injector a piezoelectric actuator can be used so that taking advantage of the so-called piezo effect a control of the needle stroke of a valve of the piezo injector made can be. The piezoelectric actuator is made of a material with a suitable Crystal structure constructed so that when planting an outer electrical voltage is a mechanical reaction that takes place in Dependence on the crystal structure and the contact areas the electrical voltage a pressure or train in a predetermined Represents direction. Piezo injectors equipped with this feature are suitable for example, for applications where strokes under high operating forces and high clock frequencies expire.

From the DE 100 26 005 A1 a piezoelectric actuator for a piezoelectric injector is described, which is used under control of a nozzle needle for the injection of fuel into the combustion chamber of an internal combustion engine of a motor vehicle. The actuation of the piezo injector is carried out by a control unit in which all operating parameters of the current vehicle state are evaluated, from which then a situational injection time results, in which the piezoelectric actuator of the piezoelectric injector is loaded. The charge on the piezoactuator keeps the piezo injector open and fuel is injected.

at the discharge phase to stop the fuel injection is the Charge of the piezoelectric actuator discharged by the control unit again.

at Faults in the control unit or in the event of a cable break the discharge of the piezoelectric actuator must be ensured possibly an uncontrolled injection of large Exclude fuel through the piezo injector. This is done by a discrete discharge resistor, the piezoelectric actuator is switched in parallel in the piezo injector. A typical resistance value is 180 kΩ. This resistance is before the encapsulation of plug contacts of the piezo injector between terminal lugs welded the plug and then encapsulated with.

Either the resistance itself as well as the required by this assembly process cause costs without these in the actual injector function to provide an equivalent.

Object of the invention

Of the Invention is based on the object, a piezo injector in such a way, that maintain the functionality of the bleeder resistor is saved and the costs caused by it or at least be reduced.

Solution of the task

The Task is a duch piezoinjector according to claim 1 solved.

Advantages of the invention

Of the Piezo injector with an electrically contactable piezoelectric actuator for Control of an actuator with which a fluid is metered, has a connector on which mounted in a contact carrier Contact elements are electrically connected to the piezoelectric actuator. The Contact elements are over the connector or the contact carrier in an electrically conductive Plastic stored so that when a blocked external discharge the piezoelectric actuator an automatic discharge of the piezoelectric actuator is possible. This feature is beneficial can be realized without separate steps in production.

In the dependent claims are advantageous measures indicated for the realization of the invention.

In Advantageously, the connector of electrical be formed of conductive plastic, the outside is accessible.

Thereby, that the connector part of a partial encapsulation of the piezo injector, there are manufacturing advantages.

By the formation of the contact carrier of electrically conductive Plastic is prevented from high-resistance contact with the surface of the piezo injector. By bridging the Contact elements with a resistance value in the range of 80-260 kΩ, preferably of 180 kΩ, can be so without further components meet safety requirements.

drawing

1 shows in a longitudinal section through a Injektorkopfteil a first embodiment and 2 in a section II-II off 1 A second embodiment of the piezo injector according to the invention.

Description of the embodiments

One in the 1 . 2 illustrated Injektorkopfteil 10 as an integral part of a piezo injector according to the invention 12 has a holding body 11 with a connection 13 for fuel, which by means of a piezaktakt shown actuator 14 can be metered. A flow channel 16 connects the piezoelectric actuator 14 with the connection 13 ,

For electrical contacting of the piezoelectric actuator 14 is on the holding body 11 an electrical connection room 17 added. In the electrical connection room 17 is a radially protruding connector 18 as part of a partial encapsulation 19 of the piezo injector 12 , a basic holder 21 , a contact carrier 22 and a filler 23 arranged. In the electrical connection room 17 are also electrical cables 24 included by contact elements 26 of the connector 18 go out and to the in the piezoelectric actuator 14 to lead. The pin-shaped contact elements 26 protrude vertically from a floor slab 27 of the connector 18 free-standing in a box-shaped receiving space 28 , which serves to receive a mating connector.

On the base carrier 21 is in a manner not shown, the electrical contact between the with the piezoelectric actuator 14 connected electrical lines 24 and the contact elements 26 arranged.

In which to the base carrier 21 subsequent contact carrier 22 are the contact elements 26 anchored, preferably by injection, and are aligned and guided by this.

The filler 23 attached to the contact carrier 22 connects, serves the volume compensation, in order for the encapsulation 19 to achieve uniform wall thicknesses.

According to a first embodiment according to 1 is the material of the encapsulation 19 and thus also the connector 18 with the bottom plate 27 through which the contact elements 26 are cohesively guided, made of an electrically conductive plastic, so that in the bottom plate 27 an electrical path between the contact elements 26 is formed.

In a second embodiment, in the 2 is visible, is in place of the encapsulation 19 this time the contact carrier 22 formed from the electrically conductive plastic, so that here the electrical path between the contact elements 26 arises.

In contrast to the first embodiment, in the second embodiment, the electrical path is isolated in the injector head part 10 of the piezo injector 12 applied and there is no high-resistance contact with the surface of the piezo injector 12 Completely.

Both embodiments have in common that the electrical resistance of the electrical path between the contact elements 26 may be in the range of 80-260 kΩ and is preferably 180 kΩ.

In the event of faults in the control unit or in the event of a cable break, the discharge of the piezoactuator may occur 14 be ensured and an uncontrolled injection of possibly large amounts of fuel through the piezo injector 12 be prevented.

QUOTES INCLUDE IN THE DESCRIPTION

This list The documents listed by the applicant have been automated generated and is solely for better information recorded by the reader. The list is not part of the German Patent or utility model application. The DPMA takes over no liability for any errors or omissions.

Cited patent literature

• - DE 10026005 A1 [0003]

Claims (6)

Piezo injector ( 12 ) with an injector head part ( 10 ), which has a holding body ( 11 ) with at least one connection ( 13 ) and flow channels ( 16 ) for supplying a fluid and at least one electrical connection space ( 17 ) and an associated connector ( 18 ) for electrically contacting a fluid-meterable piezoelectric actuator ( 14 ), in which connector ( 18 ) Contact elements ( 26 ), which are in a contact carrier ( 22 ) are anchored, characterized in that the contact elements ( 26 ) are interconnected by an electrically conductive plastic. Piezo injector according to claim 1, characterized in that the connector ( 18 ) is formed of electrically conductive plastic and an electrical path in the connector ( 18 ) between the contact elements ( 26 ) is formed. Piezo injector according to claim 2, characterized in that the connector ( 18 ) Part of a partial encapsulation ( 19 ) of the piezo injector ( 12 ). Piezo injector according to claim 1, characterized in that the contact carrier ( 22 ) consists of electrically conductive plastic and an electrical path in the contact carrier ( 22 ) between the contact elements ( 26 ) is formed. Piezo injector according to one of the preceding claims, characterized in that the contact elements ( 26 ) are bridged by the electrically conductive plastic with a resistance which is in the range 80-260 kΩ, preferably at 180 kΩ. Piezo injector according to one of the preceding claims, characterized in that the injector head part ( 10 ) integral part of the piezo injector ( 12 ).