EP1010877A2 - Stroke transmission - Google Patents

Abstract

The lift transfer device is used between a displaced drive element (3) and a lifting element (1) moved in the same direction and has at least one lever (2) resting on the drive element with lever contact points (5,7) provided by the lifting element and a bearing (4), for transferring the movement of the drive element to the lifting element via a lever effect. The lifting factor is altered as the initial stroke (xp) of the drive element increases by altering at least one lever contact point.

Description

The invention relates to an apparatus and a method for Stroke transmission between a drive element and a Lifting element.

A hub transmission is often used in an area in a separation of a drive system into a drive element and a lifting element is advantageous, for example due to a simplified production, a material technology different versions or a stroke change.

During the stroke transmission, a certain relationship is established between the secondary stroke xs of the lifting element and the primary stroke xp of the drive element, expressed by the stroke factor Π = xs / xp .
A stroke reduction, corresponding to a stroke factor Π <1, is implemented, for example, in systems in which a comparatively large-stroke motor is intended to drive a lifting element with a short travel range.
A neutral stroke transmission, corresponding to a stroke factor Π = 1, is desired, for example, if the stroke of an actuator is to be passed on precisely via a lifting element that is different in terms of material technology.
A stroke ratio occurs at a stroke factor Π> 1, for example in the case of small-stroke actuators whose stroke is to be increased via a lifting element for the necessary application safety.

For stroke transmission, in particular in the case of stroke translation from DE 195 19 191 A1 and DE 43 06 072 C2 the use of a Hydraulic chamber between the drive element and the lifting element known, the ratio of the area exposed to pressure of the drive element to the exposed surface of the Lift element directly determines the stroke factor.

A problem with stroke transmission is that a combination of different types of stroke transmission is often required, e.g. B. a neutral stroke transmission at the beginning of an operation with the following stroke ratio, z. B. in a stroke transfer from a piezoelectric actuator to a nozzle needle for operating a servo-valve-controlled fuel injector.
A high amount of force must be used to open a servo valve chamber precisely and initially. Immediately after the belching, the pressure in the valve chamber drops to a low value, so that a considerably lower force is sufficient for further opening. For the reproducibility of the opening behavior within narrow tolerances (injection quantity, start of injection), a wide opening of the valve chamber is required. Due to the small useful stroke of the piezo actuator, a stroke ratio is necessary.

A method of stroke transmission with the xp dependent primary stroke Stroke factor Π is not known.

It is the object of the present invention, one way to provide stroke transmission with variable stroke factor Π.

This object is achieved by a device according to the features of claim 1 and by means of a method according to Features of claims 13 and 14 solved. Advantageous configurations can be found in the subordinate claims.

For this purpose, a sliding drive element, one in the same direction displaceable lifting element and at least one Lever used.

ein Hebel" mindestens ein Hebel verstanden, während die Einzahl mittels genau ein Hebel" ausgedrückt wird. Unless otherwise stated, is used for a better understanding

a lever "understood at least one lever while the singular means exactly one lever "is expressed.

The lever is permanently on the drive element and can be placed on the lifting element and on a bearing. The primary stroke xp at which the lever actually rests on the lifting element and the bearing depends on the particular embodiment and on the primary stroke xp.
However, if there is a simultaneous support of the lever on the lifting element, the drive element and the bearing, this results in a lever effect, so that the primary stroke xp can be transferred to the lifting element via the lever effect of the lever. The stroke factor Π is variably adjustable, i.e. <1, = 1 or> 1.

When leverage is present, it becomes a primary driving force from the drive element via a force application point to the Lever and from there via a lifting point to the lifting element transfer. The lever rests on a pivot point on the Stock on. The area of the one-sided lever between The pivot point and force application point thus correspond to one Force arm of length L1 and the area between the lifting point and Pivotal point of a load arm of length L1 + L2, which is also called effective lever length is called.

Furthermore, the stroke transmission is designed such that the stroke factor Π can be changed at least once by changing at least one contact point with a changing primary stroke xp.
A contact point is understood to mean a pivot point, a lifting point or a force introduction point. A change in a contact point is understood to mean a change in a contact condition, that is to say both a production of a contact, e.g. B. by placing the lever, as well as changing the pivot point, lifting point or force application point.

Such a mechanical stroke transmission has the advantage that compared to a hydraulic or mechanical-hydraulic Stroke transfer to the use of a fluid chamber can be dispensed with. This results in z. B. the advantage that the secondary stroke xs largely independent of the Actuation time is.

In addition, there is the advantage of a delay-free Stroke transmission.

A very flexible geometric configuration is also expediently of the individual components possible, so that the stroke factor Π can be varied over a wide range. So he is dependent from the primary stroke xp, continuously or abruptly changeable. The stroke factor Π can e.g. B. growing, constant, falling or can be combined in any combination.

For easy adjustment of the stroke factor Π, it is advantageous if the lever always rests on a pivot point on the bearing. In the starting position, ie with a primary stroke xp = 0, the lifting element lies loosely on the drive element, and there is a distance h between the lever and the lifting element.
When actuated, the distance h is reduced by increasing the primary stroke xp until the lever touches the lifting element at a switchover point xp = xt. As a result, a lever effect of the levers can be transferred to the lifting element. In this case, the change of a contact point corresponds to the placement of the lever on the lifting element.
If the primary stroke xp is still less than or equal to the switchover point xt, ie xp ≤ xt, the stroke factor is Π = 1 due to the direct mechanical contact between the drive element and the lifting element. In contrast, x> 1 generally applies to xp> xt.

For simple construction, especially when used in a servo valve-controlled fuel injection for xp> xt a stroke factor Π between 1 (e.g. initial Opening the servo valve with high force) to 10 (e.g. wide Regurgitation preferred).

It can be favorable for easier adjustment, in the starting position the lever on the lifting element and not on the bearing put on so that there is a distance between lever and bearing. The mode of operation of such a construction is analogous to those with a distance between the lever and the lifting element.

It is advantageous for the variable adjustment of the stroke factor Π if the lever is permanently seated on the lifting element and the bearing, so that there is a mechanical frictional connection between the drive element and the lifting element via the lever over the entire lifting process. This is equivalent to the fact that the leverage effect is permanent.
In the starting position, each lever rests on the drive element via an internal force introduction point. In the starting position at xp = 0, there can also be a direct mechanical contact between the drive element and the lifting element.
When the primary stroke xp changes, the lever is moved such that the force introduction point can be changed in each case. The stroke factor Π can in turn be changed by changing the force application point.
The stroke factor Π can change at least in regions within a stroke interval {xp}, but it can also remain constant in regions.
For a rapid change in the stroke factor Π, it is advantageous if the outer force introduction points, that is to say all the force introduction points except that for xp = 0, are spatially separated from one another. This enables a sudden change in the stroke factor Π with a constant change in the primary stroke xp.

For versatile adjustment of the stroke factor Π, it is advantageous if the (inner and outer) force introduction points are arranged at least in some areas continuously, ie spatially merging. It is thus possible to vary the stroke factor Π continuously with a constant change in the primary stroke xp.
For this purpose, it is expedient if the lever rests on an at least partially curved surface of the drive element, so that a continuous change in the stroke factor Π can be set at least partially by means of the primary stroke xp.
This can advantageously be done in that the surface is alternately convex and concave, so that the stroke factor Π can be changed continuously between continuous jumps and can also assume values <1, = 1 and> 1.

It is also advantageous for precise stroke transmission if exactly one lever is available, because this makes a complex, e.g. B. due to manufacturing tolerances, adjustment the position of several levers can be avoided.

It is favorable if a primary stroke xp of 10 µm to 100 µm is executable. This is typically the case if that Drive element from a piezo actuator or a magneto or electrostrictive element is driven. Doing so Use of a ceramic multilayer piezo actuator in particular prefers.

The use of a stroke translator in a fuel injector is special because of the delay-free switching advantageous.

Figur 1 zeigt eine Vorrichtung zur Hubübertragung mit änderbarem Hubfaktor Π,

Figur 2a bis Figur 2c zeigen einen Hubübertrager in verschiedenen Stadien eines Hubvorgangs,

Figur 3a bis Figur 3c stellen die Abhängigkeit verschiedener Variablen des Hubübertragers zueinander dar,

Figur 4 zeigt eine weitere Ausführungsform eines Hubübertragers,

Figur 5 zeigt noch eine Ausführungsform eines Hubübertragers.

The stroke transmission is schematically illustrated in more detail in the following exemplary embodiments,

FIG. 1 shows a device for stroke transmission with a variable stroke factor Π,

FIGS. 2a to 2c show a stroke transmitter in different stages of a lifting process,

3a to 3c illustrate the interdependency of different variables of the stroke transmitter,

FIG. 4 shows a further embodiment of a stroke transmitter,

Figure 5 shows another embodiment of a stroke transmitter.

In Figure 1 is a sectional side view Means for stroke transmission shown in the starting position, in which two different lifting factors during a lifting process Π can be used.

A lifting element 1 sits loosely on a drive element 3. Two one-sided levers 2 are shown, each of which at a force introduction point 7 on the drive element 3 lie on. Each lever 2 is also at a pivot point 5 of a bearing 4. The levers 2 are also on one Lift point 6 can be placed on the lifting element 1, in this embodiment by attaching it to a drive element 3 facing top surface 9.

₊) gleichmäßig in einem Winkelabstand von 360°/n zueinander verteilt sein, das Hubelement 1 vollkommen rotationssymmetrisch ausgeführt sein und das Antriebselement 3 in einem Winkelabstand von 360°/n Stege als Krafteinleitungspunkte 7 aufweisen. Das Antriebselement 3 kann aber auch vollkommen rotationssymmetrisch ausgeführt sein, so daß die Krafteinleitungspunkte 7 auf einem Ring des Antriebselement 3 um die Rotationsachse I liegen. In diesem Ausführungsbeispiel werden ein vollkommen rotationssymmetrisches Antriebselement 3 und n = 3 Hebel bevorzugt. The lifting element 1 and the drive element 3 are designed such that they are geometrically similar in themselves either under any rotation about the axis of rotation I (completely rotationally symmetrical) or after a rotation through an angle of 360 ° / n (n-fold rotationally symmetrical) are transferable.
For example, n levers (n ∈

₊ ) be uniformly distributed at an angular distance of 360 ° / n from one another, the lifting element 1 is designed to be completely rotationally symmetrical and the drive element 3 has webs as force introduction points 7 at an angular distance of 360 ° / n. The drive element 3 can also be designed to be completely rotationally symmetrical, so that the force introduction points 7 lie on a ring of the drive element 3 about the axis of rotation I. In this exemplary embodiment, a completely rotationally symmetrical drive element 3 and n = 3 levers are preferred.

The distance between lifting point 6 and pivot point 5 is called Load arm of length L1 + L2 and the distance between the force application point 7 and pivot point 5 is used as a force arm of length L1 designated.

In the starting position with a primary stroke xp = 0 of the drive element 3 this is withdrawn so far that in the area the lifting point 6 a distance h between the lever 2 and the lifting element 1 exists. From xp = 0 it follows that the secondary stroke xs = 0. So there is no leverage in the starting position on the lever 2, but there is only one direct adhesion via the contact surface of lifting element 1 and drive element 3.

During an actuation process by applying a primary driving force Fp along the axis of rotation I the primary stroke xp is increased relative to the bearing 4. The primary Driving force Fp is via an actuator, e.g. B. one Piezo actuator, applied, the drive element 3 being a part of the actuator. By means of the movement of the drive element 3, the lifting element 1 by its secondary stroke xs shifted in the same direction, being a secondary Driving force Fs is forwardable.

Figure 2 shows a sectional side view schematically a stroke transmitter according to Figure 1, in the starting position (Figure 2a), at the time of touchdown Lever 2 on the lifting element 1 (Figure 2b), and after insertion the leverage (Figure 2c).

Figure 2a shows the image of the hub transmitter analogous to Figure 1 in the starting position.

Figure 2b shows the stroke transmitter when the primary stroke xp the switching point xt = h (L1 / L2) reached, in which the lever 2 come to rest at the lifting point 6 on the support surface 9 of the lifting element 1.

The movement between the states of Figure 2a and Figure 2b with increasing primary stroke xp is characterized in that due to the direct adhesion, the stroke factor Π = 1 is. Because of the displacement of drive element 3 and lifting element 1 relative to the bearing 4 decreases with increasing stroke xp or xs the distance h between lifting point 6 and lifting element 1 steadily.

As a drive means for displacing the drive element 3 can use all types of actuators or actuators become. For quick switching, especially when used in a servo-controlled fuel injector a piezo actuator as a drive means.

FIG. 2c shows the stroke transmitter with a primary stroke xp> xt.

After placing the lever 2 on the lifting element 1, there is a lever effect, so that now a stroke ratio Π = L2 / L1 , here: Π> 1, is present. When the stroke ratio is raised, the lifting element 1 lifts off the drive element 3 and is displaced solely on the basis of the leverage effect.
To avoid an undesirable displacement of the lifting element 1 in the event of a thermally induced change in the length of the drive element 3, a distance between the drive element 3 and the lifting element 1 can be provided in addition to the distance h in the starting position.

It is therefore possible to use only the stroke xp of the drive element 3 dependent secondary stroke xs trigger. Compared to a hydraulic or mechanical-hydraulic Stroke transmission is this purely mechanical stroke transmission independent of fluid. This results in z. B. the advantage that the secondary stroke xs largely independent of the duration of actuation is.

Figure 3 shows a by means of a piezoelectric actuator driven drive element 3 an application of the secondary stroke xs against the primary stroke xp (Figure 3a), a plot the secondary driving force Fs of the lifting element 1 against the Primary stroke xp (Figure 3b) and a plot of the secondary Driving force Fs against the secondary stroke xs (Figure 3c), respectively for a pure lever drive with stroke factor Π = 2 (roughly dashed), a purely mechanical direct drive (finely dashed) with stroke factor Π = 1 and a stroke transmitter after Figures 1 and 2 with stroke factor Π = 1 and Π = 2 (solid Line).

In Figure 3a it is documented that initially the stroke transmitter with the same stroke factor Π = 1 as the Direct drive and after reaching the switchover point xt = 10 (in any units) to the stroke factor Π = 2 of the lever drive toggles.

Figure 3b shows that until the switch point xt is reached the values of the stroke transmitter are those of the direct drive correspond and quickly after reaching the switching point xt drop to the values of the pure lever drive.

In Figure 3c it is shown that after reaching the switch point xt is the secondary driving force Es of the stroke transmitter drops below the value for the lever drive, the difference due to the original distance h between levers 2 and lifting element 1 on the stroke transmitter.

It can thus be clearly seen from FIGS. 3a to 3c that by means of the stroke transmitter at the beginning of the actuation process a high force is transferable, and after switching to one purely lever-assisted drive mode the path characteristic a pure lever drive is used.

Figure 4 shows a sectional side view Another embodiment of a stroke transmitter in the starting position.

In the starting position, the at least two levers 2 lie on one inner force introduction point 71 on the drive element 3 on. At the same time, the lifting element 1 rests on one Lift point 6 on the levers 2 and at a pivot point 5 on the Camp 4 on. Thus, the lever 2 becomes a mechanical one Non-positive connection between the drive element 3 and the lifting element 1 mediates.

The inner force introduction point 71 and the lifting point 6 one Lever 2 lie on a line parallel to the axis of rotation I. This ensures that only when the lever 2 is attached the length L1 of the force arm at the inner force introduction point 71 corresponds to the total effective lever length L1 + L2, so that because of the lack of leverage, a neutral stroke transmission Π = 1 occurs.

During an actuation process, the drive element 3 is along the axis of rotation I shifted relative to the bearing 4. Because the length L1 of the power arm is equal to the effective length L1 + L2 of lever 2, lever 2 does not Leverage creates, but the primary stroke xp directly Transfer to the lifting element 1 without loss of stroke. At the same time are by the movement of the lifting element 3 relative to the Bear the levers 2 in the direction of the drive element 3 rotated, the inner force application point 71 as Pivotal effect.

As soon as the primary stroke xp is so great that the lever 2 on another, external force introduction point 72, ..., 7n (n ∈ ₊ ) as the inner force introduction point 71 (i.e. a contact point changes), the length L1 of the force arm changes, which is now smaller than the length L1 + L2 of the load arm.
The lever 2 is a stroke factor Π = 1 + L2 / L1 given, so that with increasing primary stroke xp the levers 2 stand out from the internal force introduction point 71.

In this embodiment there is exactly one more Force introduction point 72, which is further from the axis of rotation I is removed as the internal force application point 71. It can but in another form of performance any n outer Force application points 71, 72, ..., 7n are used, whereby usually n with the distance from the axis of rotation I grows.

With further displacement of the drive element 3 after mounting to an external force introduction point 72, ..., 7 (n-1) can each lever 2 successively on further external force introduction points 73, ..., 7n put on, each time the Length of the power arm L1 abruptly reduced. By means of a such an arrangement can have n stroke ratios Π depending be adjusted by the primary stroke xp.

5 shows another embodiment in the starting position shown as a sectional view in side view.

In contrast to FIG. 4, there are no discrete force introduction points 71, ..., 7n more available, rather set the levers 2 on a curved surface of the drive element 3, which corresponds to an assignment n → ∞.

This ensures that when the drive element is displaced 3 a continuous change in length L1 of the power arm is possible.

The surface can also be curved such that a neutral stroke transmission takes place when the drive element 3 is displaced.
The surface can also be shaped such that the stroke factor Π only changes continuously in sections, for example in that the surface is concave and convex in sections in the direction of the lifting element 1.

To improve the variation of the stroke factor Π, it is advantageous if the at least one lever 2 is also a curved, at least on one contact point 5,6,7,71, ..., 7n, 71 ', ..., 7n' has an overlying surface.

It is also advantageous if exactly one lever 2 is used we because then an adjustment of several levers 2 to Ensuring an equal leverage effect does not apply. A possible decentering of the lifting element 1 can be done by means of a Guide the lifting element 1, z. B. in a hole, largely be balanced.

All versions known from lever technology are suitable as lever bearings, e.g. B. cutting edge bearings or roller and bending bearings and combinations thereof.
An initial direct frictional connection between the drive element (3) and the lifting element (1) can also take place via cams passing laterally past the levers (2).

Claims (14)

Stroke transmission device, comprising a displaceable lifting element (1) and a drive element (3) displaceable in the same direction, at least one lever (2) which rests on the drive element (3) and which can be placed on the lifting element (1) and on a bearing (4),
in which with simultaneous support of the at least one lever (2) on the lifting element (1), the drive element (3) and the bearing (4), a primary stroke (xp) of the drive element (3) via a lever effect of the levers (2) on the lifting element (1) is transferable, and with changing primary stroke (xp) a stroke factor (Π) can be changed by changing at least one contact point (5,6,7,71, ..., 7n, 71 ', ..., 7n') of at least one lever (2) . Hub transmission device according to claim 1, wherein the at least one lever (2) rests on the bearing (4) at a pivot point (5), and in the starting position, the lifting element (1) and the drive element (3) sit loosely on one another, and there is a distance (h) between the lever (2) and the lifting element (2), and the distance (h) can be reduced by means of an expandable primary stroke (xp) until the primary stroke (xp) can be transferred to the lifting element (1) via a lever effect from at least one lever (2) being placed on the lifting element (1). Hub transmission device according to claim 1, wherein the at least one lever (2) rests on the lifting element (1) at the lifting point (6), and in the starting position, the lifting element (1) and the drive element (3) sit loosely on top of each other, and there is a distance between the lever (2) and the bearing (4), and by means of an expandable primary stroke (xp), the distance can be reduced until at least one lever (2) is placed on the bearing (4), the primary stroke (xp) can be transferred to the lifting element (1) via a lever effect. Hub transmission device according to claim 1, wherein the at least one lever (2) is seated on the lifting element (1) and the bearing (4), so that there is a mechanical frictional connection between the drive element (3) and the lifting element (1) via at least one lever (2),
in which in the starting position, the at least one lever (2) rests on an inner force introduction point (71, 71 ') of the drive element (3), when the stroke (xp) of the drive element (3) changes, the levers (2) can be moved so that they can each be placed on an external force introduction point (72, ..., 7n, 72 ', ..., 7n'), so that the stroke factor (Π) can be changed at least in certain areas. Hub transmission device according to claim 4, wherein the outer force introduction points (72, ..., 7n) from each other are spatially separated. Hub transmission device according to claim 4, wherein the outer force introduction points (72 ', ..., 7n') at least to merge spatially continuously into each other. Apparatus according to claim 6, wherein the levers (2) each on an at least partially curved Surface of the drive element (3) rest so that by means of the stroke (xp) of the drive element (3) at least in some areas a continuous change in the stroke factor (Π) is adjustable. Device according to one of the preceding claims, which has exactly one lever (2). Device according to one of the preceding claims, by means of the drive element (3) a stroke (xp) of 10 µm to 100 µm is executable. Device according to one of the preceding claims, which the stroke factor (Π) is in the range between 1 and 10. Device according to one of the preceding claims, the drive element (3) by means of a ceramic multilayer piezo actuator is movable. Device according to one of the preceding claims for Use in a fuel injector. A method of operating an apparatus according to claim 2, wherein during an actuation process from the starting position, the drive element (3) displaces the lifting element (1) while reducing the distance (h) without loss of stroke until the at least one lever (2) rests on the lifting element (1), whereupon the magnification increases Primary stroke (xp) the lifting element (6) is shifted by the power transmission transmitted by the drive element (3) via the lever (2). A method of operating an apparatus according to claim 5, wherein

during an actuation process from the starting position, the drive element (3) moves the lifting element (1) over the at least one lever (2) for as long as the stroke is neutral, until the stroke element (1) is displaced in a stroke-translated manner by a change from an inner force introduction point (71) to an outer force introduction point (72, ..., 7n), which further increases the primary stroke (xp).

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