EP1010877B1 - Stroke transmission - Google Patents

Description

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

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 change of stroke.

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 much 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 xp dependent on the 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 the 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.

If nothing else is stated, it will be better understood "one lever" means at least one lever, while the number is expressed using "exactly one lever".

The lever is constantly 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 in such a way that with a changing primary stroke xp, the stroke factor Änderung can be changed at least once by changing at least one contact point.
A contact point is understood to mean a fulcrum, a lifting point or a force application 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 expedient 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 changeover 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 injector 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 falls if the lever is constantly 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 is permanent.
In the starting position, each lever rests on the drive element via an inner 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 so that the force introduction point can be changed in each case. The stroke factor Π can 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 for that for xp = 0, are spatially separated from one another. In this way, a sudden change in the stroke factor Π can be achieved 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 continuously, that is to say spatially merging, at least in some areas. 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 favorable if the lever rests on an at least partially curved surface of the drive element, so that a continuous change in the stroke factor fakt can be set at least in regions 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 between continuous jumps can be changed continuously 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, z. 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, with two different lifting factors during one lifting process Π can be used.

A lifting element 1 sits loosely on a drive element 3. Two unilateral levers 2 are shown, each of which at a force introduction point 7 on the drive element 3 rest. 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 with 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 each other, the lifting element 1 is designed to be completely rotationally symmetrical and the drive element 3 has webs at an angular distance of 360 ° / n as force introduction points 7. The drive element 3 can also be made 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 frictional connection over 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 Switchover point xt = h · (L1 / L2) reached, at which the lever 2 at the lifting point 6 on the support surface 9 of the lifting element 1 Edition come.

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 levers 2 on the lifting element 1, there is a lever effect, so that there is now a stroke ratio Π = L2 / L1, here: Π> 1. In the case of stroke transmission ratio, 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 fluid independently. This gives 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 switches.

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 Fs of the stroke transmitter drops below the value for the lever drive, the difference due to the original distance h between the 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 conveyed.

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 when the lever 2 is attached only 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 moved 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 stroke loss. simultaneously 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 thus gives a stroke factor Π = 1 + L2 / L1, so that the levers 2 stand out from the inner force introduction point 71 as the primary stroke xp continues to increase.

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 inner 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, with 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 so 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.

For improved 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)

1. Device for transferring lift, having

   a movable lifting element (1) and a drive element (3) which can be moved in the same direction,

   at least one lever (2), which in each case rests on the drive element and which in each case can be placed on the lifting element (1) and on a bearing (4),

   wherein

   if the lever (2), of which there is at least one, simultaneously rests on the lifting element (1), the drive element (3) and the bearing (4), a primary lift (xp) of the drive element (3) can be transferred by leverage of the levers (2) to the lifting element (1), and

   with a changing primary lift (xp) a lift 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).
2. Device for transferring lift according to Claim 1, in which

   the lever (2), of which there is at least one, in each case rests on a pivot point (5) on the bearing (4), and

   in their initial position the lifting element (1) and the drive element (3) are seated movably on one another, and there is a distance (h) between the lever (2) and the lifting element (2), and

   by means of an expandable primary lift (xp) the distance (h) can be reduced until once at least one lever (2) has been placed on the lifting element (1) the primary lift (xp) can be transferred by leverage to the lifting element (1).
3. Device for transferring lift according to Claim 1, in which

   the lever (2), of which there is at least one, in each case rests at the lifting point (6) on the lifting element (1), and

   in their initial position the lifting element (1) and the drive element (3) are seated movably on one another, and

   there is a distance between the lever (2) and the bearing (4), and

   by means of an expandable primary lift (xp) the distance (h) can be reduced until once at least one lever (2) has been placed on the bearing (4) the primary lift (xp) can be transferred by leverage to the lifting element (1).
4. Device for transferring lift according to Claim 1, in which

   the lever (2), of which there is at least one, sits on the lifting element (1) and the bearing (4), so that a mechanical frictional connection exists between drive element (3) and lifting element (1) via at least one lever (2),

   whereby

   in their initial position the lever (2), of which there is at least one, in each case rests on an inner force application point (71, 71') of the drive element (3),

   in the event of a change in the lift (xp) of the drive element (3) the levers (2) can be moved such that in each case they can be placed on an outer force application point (72, ... , 7n, 72', ... , 7n'), so that the lift factor (Π) can be changed at least in terms of range.
5. Device for transferring lift according to Claim 4, in which the outer force application points (72, ... , 7n) are spatially separated from one another.
6. Device for transferring lift according to Claim 4, in which the outer force application points (72', ... , 7n') continuously merge into one another spatially in terms of range.
7. Device according to Claim 6, in which the levers (2) in each case rest on a surface of the drive element (3), which is curved at least in terms of range, so that by means of the lift (xp) of the drive element (3) a continuous change in the lift factor (Π) can be set at least in terms of range.
8. Device according to one of the preceding claims, in which exactly one lever (2) is present.
9. Device according to one of the preceding claims, in which by means of the drive element (3) a primary lift (xp) of 10 µm to 100 µm can be effected.
10. Device according to one of the preceding claims, in which the lift factor (Π) is in the range between 1 and 10.
11. Device according to one of the preceding claims, in which the drive element (3) can be moved by means of a ceramic multi-layer piezo-actuator.
12. Device according to one of the preceding claims, for use in a fuel injector.
13. Method to operate a device according to Claim 2, in which in the event of an actuation procedure from the their initial position, the drive element (3) moves the lifting element (1) with no loss of lift, while reducing the distance (h), until the lever (2), of which there is at least one, is placed on the lifting element (1), in response to which, as the primary lift (xp) increases further, the lifting element (6) is moved by the frictional connection transferred from the drive element (3) via the lever (2) with transmission of lift.
14. Method for operating a device according to Claim 5, in which
    in the event of an actuation procedure from the initial position, the drive element (3) moves the lifting element (1) via the lever (2), of which there is at least one, with neutral transmission of lift, until
    by a change from an inner force application point (71) to an outer force application point (72, ... , 7n), as the primary lift (xp) increases further, the lifting element (1) is moved with transmission of lift.

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