Electrical generator or motor structure – Non-dynamoelectric – Piezoelectric elements and devices
Reexamination Certificate
2003-10-20
2004-09-07
Dougherty, Thomas M. (Department: 2834)
Electrical generator or motor structure
Non-dynamoelectric
Piezoelectric elements and devices
C310S331000, C310S355000, C310S316010, C310S323010, C029S025350, C123S470000, C251S129110
Reexamination Certificate
active
06787973
ABSTRACT:
TECHNICAL FIELD OF THE INVENTION
The invention relates to a device for transmitting an excursion of an actuator and a method for its production according to the independent Claims.
BACKGROUND OF THE INVENTION
Actuators based on the piezoelectric principle are suitable for the highly precise and very rapid regulation of control processes, as are expedient for example for the activation of injection devices or valves in internal combustion engines. In order to achieve larger linear excursions of the piezoactuators, these have to comprise a number of individual piezoelements stacked one on top of the other. This has the disadvantage that the size of the structure assumes dimensions that are not permissible for many intended uses. For example the space for incorporating injection valves in the cylinder head of an internal combustion engine is limited so that there is generally no room for piezoactuators with the longitudinal dimension required for the required control motions. Smaller piezoactuators are therefore used, the linear excursions of which are translated by means of suitable lever devices into larger control member excursions.
An injection valve is known from U.S. Pat. No. 4,101,076 comprising a piezoelectric actuator, which activates an injection needle directly via a mechanical transmission element. The transmission element has two lever arms of different lengths, disposed at right angles to each other and connected to each other in a bearing area. The shorter lever arm is assigned to the piezoelectric actuator and the longer lever is assigned to the injection needle. The transmission element rests on the housing of the injection valve in the bearing area The excursion of the piezoelectric actuator is converted by the different lengths of the two lever arms into a larger excursion of the injection needle.
However the form of the transmission element offers only moderate rigidity, which results in imprecise excursion transmission in particular with highly dynamic circuit processes.
An injection valve is also known from WO 99/17014, with which mechanical transmission elements are provided for the transmission and translation of an excursion of a piezoactuator to a control member, said transmission elements essentially having the form of a cylinder, the limiting surfaces of which are configured in an essentially triangular manner, with the corners rounded. The width of the transmission elements causes planar bearing areas to be formed so that friction during transmission is reduced.
SUMMARY OF THE INVENTION
The object of the present invention is to provide a device for transmitting an excursion of an actuator, which is simple and small in structure and allows transmission and translation of actuator excursion to a control member with the lowest possible level of friction.
According to the invention, the device for transmitting an excursion of an actuator comprises at least one transmission element having a first, a second and a third bearing area, wherein the first bearing area is assigned to a counter bearing, the second bearing area is assigned to the actuator and the third bearing area is assigned to a control member. According to the invention, the at least one transmission element is supported with the first bearing area against the counter bearing when the actuator is operated and said transmission element moves the control member with the third bearing area by means of a rotational motion about a point of rotation, with the at least one transmission element being configured essentially in the form of a plate, which is disposed substantially perpendicular to the control motion and with the first, second and third bearing areas each being configured in the form of substantially straight surfaces on the plate.
The device according to the invention in particular has the advantage of minimizing the relative motion between the transmission elements, so that direct transmission of the excursions of the actuator is ensured with little wear and loss.
A distance between a central axis of the actuator and a central axis of the control member may be provided, with which the advantage of a relatively compact structure of the transmission element is associated, said transmission element being disposed between the actuator and the control member.
At least two transmission elements can be disposed opposite each other, which has the advantage of symmetrical distribution of the control forces both at the actuator and at the control member. Also with two transmission elements the control forces acting on each of these transmission elements are halved, as are the compressive loads acting at the respective bearing areas.
At least three transmission elements can be provided, which are disposed essentially concentrically in respect of each other. This has the advantage of further reducing the control forces and therefore the compressive loads at the respective bearing areas. Also with three or more transmission elements, these can be relatively compact in design, as they have to transmit less force in total.
Concentric central axes of the actuator and the control member can be provided, which has the advantage that the entire device is very compact. A fuel injector with the control device according to the invention can thus be relatively slim in design and is therefore also suitable for incorporation in very restricted spatial conditions, e.g. in the cylinder head of an internal combustion engine.
The plate of the at least one transmission element can be configured in a stepped manner. This embodiment according to the invention has the advantage of an ideally compact structural design, as it means that the distance between the actuator and the control member can be very small.
The second bearing area can be assigned to an upper side and the third bearing area can be assigned to a lower side of a first straight section of the stepped plate, which has the particular advantage of a very compact transmission element.
The second straight section of the stepped plate may partially encompass a lower sleeve area of the actuator, which also has the advantage of a very compact transmission element structure.
The plate can be produced by cold or hot forming. This has the particular advantage of favorable fiber orientation in the plate and therefore a very high level of strength in respect of plastic deformation subject to the operational loads occurring.
Ground surfaces of the bearing areas of the plate can be provided, with the advantage of minimizing friction between the surfaces of the bearing areas in contact.
An intermediate member connected to the actuator can be provided between the actuator and the second bearing area of the at least one transmission element. This embodiment has the advantage of an intermediate member which can be easily adapted to spatial conditions, thus contributing overall to a compact structure of the device according to the invention.
A positive, non-positive or material-fit connection between the actuator and intermediate member can be provided, which has the advantage that no further connection elements are required. This results in a light weight and a compact structure.
A linear contact between the raised edge of the intermediate member and the second bearing area of the plate can be provided, which has the advantage of good distribution of the forces occurring. Compared with point bearing, linear contact has the advantage of significantly lower compressive loads.
The height of the raised edge can be approximately 200 &mgr;m. This ensures that a defined bearing line remains even in unfavorable conditions, which is not subject to such elastic or plastic deformation that the defined bearing line becomes an undefined bearing area.
The raised edge can be rounded, which has the advantage of continued linear contact even with angular motions.
Alternatively, the second bearing area of the at least one plate may have at least one raised edge, which is in contact with the intermediate member. This ensures that a defined bearing line remains even in unfavorable conditions,
Frank Wilhelm
Komischke Thomas
Kronberger Maximilian
Schmidt Harald
Aguirrechea J.
Baker & Botts L.L.P.
Dougherty Thomas M.
Volkswagen Mechatronic GmbH & Co.
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