Machine element or mechanism – Control lever and linkage systems – Variable output force
Reexamination Certificate
1999-12-20
2002-04-09
Bucci, David A. (Department: 3682)
Machine element or mechanism
Control lever and linkage systems
Variable output force
C074S518000, C251S129060, C310S328000
Reexamination Certificate
active
06367350
ABSTRACT:
BACKGROUND OF THE INVENTION
The invention relates to an apparatus and a method for stroke transmission between a drive element and a stroke or reciprocating element.
A stroke transmission is often used in areas where it may be advantageous to separate a drive system into a separate drive element and stroke element. For example, this may be done to simplify a manufacturing process, to permit use of different materials in different parts of the drive system, or to simply provide a change of stroke or ratio.
In the stroke transmission, a particular ratio is set between the secondary stroke (xs) of the stroke element and the primary stroke (xp) of the drive element, expressed by the stroke factor (II), where II=xs/xp.
A stroke gear reduction, corresponding to a stroke factor II<1, is realized for example in systems in which a comparatively large-stroke motor is supposed to drive a stroke element having a small travel.
A neutral stroke transmission, corresponding to a stroke factor II=1, is for example desirable if the stroke of an actuator is supposed to be communicated precisely via a stroke element that is realized differently in terms of materials.
A stroke gearing up or multiplication occurs when there is a stroke factor II>1, for example given small-stroke actuators whose stroke is supposed to be enlarged via a stroke element for the necessary application.
For stroke transmission, in particular for stroke gearing up, German patent documents DE 195 19 191 A1 and DE 43 06 072 C2 disclose the use of a hydraulic chamber between the drive element and the stroke element is known, whereby the ratio of the surface of the pressure-exposed drive element to the surface of the pressure-exposed stroke element directly determines the stroke factor.
A problem in stroke transmission is that a combination of different types of stroke transmission is often required. A neutral stroke transmission is often needed at the beginning of an actuation process with a subsequent stroke gearing up, e.g., given a stroke transmission from a piezoelectric actuator to an injector needle or vale needle for the operation of a servo-valve-controlled fuel injector.
In this context, a large force has to be applied for the initial precise opening of a servo-valve chamber. Immediately after this application of force, the pressure in the valve chamber falls to a low value, so that a significantly smaller force is sufficient of the further opening. For the reproducibility of the opening behavior within narrow tolerances (injection quantity, beginning of injection), a wide opening of the valve chamber is required. Due to the small useful stroke of the piezoactuator, a stroke gearing up is necessary for this purpose.
SUMMARY OF THE INVENTION
A stroke transmission apparatus and a stroke transmission method are not known wherein a stroke factor II is dependent on a primary stroke xp of a drive element.
One object of the present invention is to provide a stroke transmission capable of providing a variable stroke factor II. Another object of the present invention is to provide a stroke transmission method capable of providing a variable stroke factor II.
These and other objects, features and advantages of the present invention are achieved by a stroke transmission apparatus and a method of transmitting stroke.
For this purpose, a displaceable drive element, a stroke element that can be displaced in the same direction, and at least one lever are used.
Unless otherwise indicated, for better understanding “a lever” is to be understood as referring to at least one lever, while the singular is expressed by “exactly one lever.”
The lever is applied continuously to the drive element, and can be placed on or in contact with the stroke element and a bearing. The primary stroke xp in which the lever is actually placed on the stroke element and the bearing depends on the respective specific embodiment and on the primary stroke xp.
However, if a simultaneous seating or contact of the lever on the stroke element, the drive element, and the bearing is present, a lever effect results, so that the primary stroke xp of the drive element can be transmitted to the stroke element via the lever action of the lever. The stroke factor II can thereby vary between a gearing up transmission (<1), a neutral transmission (=1) or a gear reduction transmission (>1).
When the lever effect is present, a primary drive force is transmitted from the drive element to the lever via a force introduction point, and from the lever it is transmitted to the stroke element via a stroke point. The lever is supported on the bearing at a pivot point. The region on the one side of the lever between pivot point and force introduction point thus corresponds to a power arm of length L
1
, and the region between the stroke point and pivot point corresponds to a work arm of length L
1
+L
2
, which is also designated the effective lever length.
In addition, the stroke transmission is formed in such a way that as the primary stroke xp changes, the stroke factor II can be modified at least once by modifying at least one contact point. A contact point is to be understood as a pivot point, a stroke point or a force introduction point.
Such a mechanical stroke transmission has the advantage that, in contrast to a hydraulic or mechanical-hydraulic stroke transmission, the need for a fluid chamber can be eliminated. In this way one advantageous result is that the secondary stroke xs is largely independent of the duration of actuation.
In addition, another advantageous result is that of a stroke transmission free of delay.
A very flexible geometrical construction of the individual components is also advantageously possible, so that the stroke factor II can be varied within a wide range and dynamically. Thus, dependent on the primary stroke xp, it can be varied continuously or discontinuously. The stroke factor II can for example be set to increase, to be constant, to decrease, or to include any combination of these.
For the simple adjustment of the stroke factor II, it is advantageous if the lever is respectively applied continuously to a pivot point on the bearing. In the initial position, i.e. given a primary stroke xp=0,the stroke element is placed loosely on the drive element, and there is a spacing (h) or gap between the lever and the stroke element.
Given an actuation by means of an increase of the primary stroke xp, the spacing h is reduced until the lever rests at a changeover point xp=xt when h=0 on the stroke element. At this point, a lever effect of the lever can be transmitted to the stroke element. In this case, the modification of a contact point thus corresponds to the seating of the lever on the stroke element.
If the primary stroke xp is even smaller than or is equal to the changeover point (xt), i.e. xp ≦xt, then the stroke factor II=1, dye to the direct mechanical contact between the drive element and the stroke element. In contrast, it is also generally true that the stroke factor II>1 for xp>xt.
For the simple construction, in particular given use in a servo-valve-controlled duel injector, for xp>xt a stroke factor II between 1 (e.g., initial opening of the servovalve with large force) to 10 (e.g. wide subsequent application of force) is preferred.
For simpler adjustment, it can be advantageous in the initial position to place the lever on the stroke element and not on the bearing, so that a spacing results between the lever and the bearing. The manner of action of such a construction is analogous to that with a spacing between the lever and the stroke element. For example, if xp is less than or equal to xt, then the stroke factor II is again equal to 1 because the drive element and stroke element are in direct mechanical contact.
For the variable adjustment of the stroke factor II, it is advantageous if the lever sits permanently on the stroke element and on bearing, so that a mechanical non-positive, or frictional, or a surface to surface connection is present between the drive elem
Gottlieb Bernhard
Kappel Andreas
Meixner Hans
Mock Randolf
BakerBotts LLP
Bucci David A.
Kim Chong H.
Siemens Aktiengesellschaft
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