Abstract:
An apparatus for the transmission of a deflection of an actuator, in particular of a piezoelectric actuator of an injection valve, comprises at least one first lever device which has a first transmission element which transmits the deflection of the actuator. In this case, there is provision for at least one first spring element to be provided for guiding or mounting the first transmission element.

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
   This application is a continuation of co-pending International Application No. PCT/EP04/00975 filed Feb. 3, 2004, which designates the United States and claims priority to German Application No. DE 103 04 240.7 filed Feb. 3, 2003, the contents of which are hereby incorporated by reference in their entirety. 

   TECHNICAL FIELD 
   The invention relates to an apparatus for the transmission of a deflection of an actuator, in particular of a piezoelectric actuator of an injection valve, with at least one first lever device which has a first transmission element which transmits the deflection of the actuator. 
   BACKGROUND 
   Actuators based on the piezoelectric principle are suitable for the highly accurate and very rapid control of actuating operations, such as are expedient, for example, for the activation of injection apparatuses or injection valves of internal combustion engines. In order to implement pronounced linear deflections of the piezoelectric actuators, these must consist of a multiplicity of individual piezoelectric elements stacked one on top of the other. The disadvantage of this is that the overall size assumes inadmissible dimensions for many applications. Thus, for example, the installation space for injection valves in the cylinder head of an internal combustion engine is limited in such a way that there is, as a rule, no room for piezoelectric actuators in the length dimension necessary for the desired actuating movements. For this reason, smaller piezoelectric actuators are used, the linear deflections of which are stepped up into larger deflections by suitable lever devices. 
   WO 99/17014 discloses, for example, an injection valve in which, for transmitting a deflection of a piezoelectric actuator to an actuating member and for stepping up this deflection, mechanical transmission elements are provided, which are essentially in the form of a cylinder, the boundary surfaces of which are of essentially triangular design, the corners being rounded. Sheetlike bearing regions are in this case formed as a result of the width of the transmission elements. 
   For example in conjunction with control valves for injection apparatuses, it is necessary for the actuator space to be sealed off with respect to other regions of the control valve. O-rings have already been used for this purpose. The use of O-rings presents problems, however, in as much as O-rings can be damaged relatively easily. This problem is aggregated further in that damage to an O-ring cannot readily be detected reliably during subsequent tests. 
   Compared with O-ring sealing off, a metallic sealing off of the actuator space therefore affords advantages, and, in preferred embodiments, there may be provision for the sealing surfaces to run perpendicularly with respect to the actuator axis. The surface pressure required for the sealing function may be applied, for example, via a connecting thread. In embodiments of this type with a metallic sealing off of the actuator space, however, there is the problem that the guide of the transmission element is not fastened nonpositively with respect to the actuator, but can move spatially within the play tolerance. This moveability may cause kinematic variations and therefore dispersions in the stroke step-up. 
   SUMMARY 
   The object on which the invention is based is to develop the generic apparatuses for the transmission of a deflection of an actuator, in such a way that an insensitive construction is achieved and undesirable dispersions of the stroke step-up are avoided or at least reduced. 
   This object is achieved by an apparatus for the transmission of a deflection of an actuator, in particular of a piezoelectric actuator of an injection valve, comprising at least one first lever device which comprises a first transmission element which transmits the deflection of the actuator, and a spring element for guiding the first transmission element, wherein the first transmission element is supported on a plate, the spring element is tension-mounted between a first housing portion and the plate, and the spring element prestresses the plate against a second housing portion. 
   The plate may constitute a stop for an actuating member to be actuated by the piezoelectric actuator. The plate can be designed as a guide plate, wherein the guide plate orients in position a second lever device with a second transmission element, wherein the second transmission element lies with a bearing region on the second housing portion and with a further bearing region on the actuating member, and wherein the second transmission element is operatively connected to the first transmission element for the actuation of the actuating member. The spring element can be of essentially circular design and may have a guide orifice in which the first transmission element is introduced and positioned. The spring element may have a circular edge region which bears against the first housing portion, and the edge region may have recesses. The spring element may have a downwardly curved edge region which runs around and which lies on the guide plate. The plate can be designed as a guide plate in the form of a circular disk, and the guide plate may have a recess in which the second transmission element is arranged. A second spring element can be provided for guiding or mounting the first transmission element. The spring element and/or the second spring element may have a flat spring characteristic curve in relation to the force generated in each case. The actuator can be assigned a first housing portion and the first lever device and/or the second lever device are/is assigned a second housing portion, the first housing portion and the second housing portion may be sealed off via at least one sealing surface running approximately perpendicularly with respect to the deflection direction of the actuator. 
   The apparatus according to the invention for the transmission of a deflection of an actuator builds on the generic prior art in that at least one spring element is provided for guiding or mounting the first transmission element. By means of the spring element, the first transmission element is brought into a defined position with respect to the actuator, preferably with little or no play tolerance, so that dispersions of the stroke step-up can be avoided or at least reduced. Moreover, by means of the spring element, a plate on which the first transmission element lies is prestressed relative to the housing. In a preferred embodiment, the plate constitutes a stop for the actuating member. In a further preferred version, the plate is designed as a guide plate and the guide plate guides a second transmission element which is arranged between the first transmission element and the actuating member. 
   In particularly preferred embodiments of the apparatus according to the invention for the transmission of a deflection of an actuator, there is provision for a second spring element to be provided for guiding or mounting the first transmission element. 
   In the case of a suitable design of the first and of the second spring element, this solution allows an automatic adjustment of the first transmission element and therefore an automatic setting of the stroke step-up. 
   In preferred embodiments of the apparatus according to the invention, there is provision, furthermore, for the first spring element and/or the second spring element to be prestressed, in the mounted state of the apparatus, in order to generate the first force and/or the second force. This solution comes under consideration particularly when the actuator and further components of the apparatus are assigned different housing portions which are connected to one another during the mounting of the apparatus, for example by means of the tightening of a fastening nut, and the first spring element and/or the second spring element are/is arranged in the region between the different housing portions. 
   Particularly in the connection explained above, there is advantageously provision, furthermore, for the first spring element and/or the second spring element to be prestressed by means of a third force and/or a fourth force which comprise or comprises a force component running approximately parallel to the deflection direction of the actuator. Such a prestressing of the first spring element and/or of the second spring element may be achieved, for example, if, in the unbraced state, the spring elements project beyond the interfaces of a housing portion, and the housing portion is brought into contact with an adjacent housing portion, for example as a result of the tightening of a fastening nut, so that, after the fastening nut has been tightened, the spring elements lie with an end portion in the connecting plane of the housing portions. 
   Particularly when the housing portions are to be connected, while at the same time being sealed off, it is preferred, furthermore, that the first spring element and/or the second spring element or the third spring element have or has a flat spring characteristic curve in relation to the force generated in each case. In this instance, the sealing force, due to the prestressing forces, is reduced, and therefore the latter must fulfill high accuracy requirements. In a particularly preferred embodiment, the spring elements are designed in such a way that the forces exerted on the first transmission element by these are exactly zero, and, if appropriate, there may be a slight play between at least one spring element and the first transmission element. 
   In particularly preferred embodiments of the apparatus according to the invention for the transmission of a deflection of an actuator, there is provision, furthermore, for it to have a second lever device which comprises a second transmission element, the deflection of the first transmission element being transmitted to the second transmission element. In this instance, there are two lever devices which are arranged in series and by means of which the stroke step-up ratio can be increased even further. 
   In this instance, it is preferred that the first transmission element is arranged between the actuator and the second transmission element with respect to the deflection direction of the actuator, and that the second transmission element is guided by at least one guide plate. 
   In this instance, in a preferred development of the invention, the third spring element or the first spring element and/or the second spring element are or is designed in such a way that a fifth force generated by them and exerted on the at least one guide plate is determined by the spring characteristic of the first spring element and/or of the second spring element or of the third spring element. 
   In all the embodiments of the apparatus according to the invention, there may be provision for the first spring element and/or the second spring element to be essentially L-shaped, at least in the prestressed state, a V-shaped portion being provided in the long leg of the L. The L-shape or V-shape may, if appropriate, also refer to the cross section through a spring element, for example when only one annular spring element is used. 
   Embodiments of the apparatus according to the invention are considered to be particularly advantageous in which there is provision for the actuator to be assigned a first housing portion and for the first lever device and/or the second lever device to be assigned a second housing portion, the first housing portion and the second housing portion being sealed off via at least one sealing surface running approximately perpendicularly with respect to the deflection direction of the actuator. In this case, in particular, there may be provision for the spring element or the first spring element and/or the second spring element to project beyond the sealing surface in the unbraced state and to be prestressed as a result of the tightening of a fastening nut according to the spring characteristic curve and the projection. 
   The invention makes it possible to dispense with additional components, such as, for example, a cup spring, and, even in series production, to ensure a prestressing force having a narrow tolerance. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The invention, then, is explained by way of example by means of a preferred embodiment, with reference to the accompanying drawings in which: 
       FIG. 1  shows a diagrammatic illustration of an embodiment of the apparatus according to the invention; 
       FIG. 2A  shows the first transmission element in an equilibrium of forces; 
       FIG. 2B  shows the first spring element in an equilibrium of forces; 
       FIG. 2C  shows the second spring element in an equilibrium of forces; 
       FIG. 3A  shows a top view of the spring elements of  FIGS. 1  and also  2   b  and  2   c  according to a first embodiment; 
       FIG. 3B  shows a top view of the spring elements of  FIGS. 1  and also  2   b  and  2   c  according to a second embodiment; 
       FIG. 3C  shows a top view of the guide plate and the second transmission element; 
       FIG. 3D  shows a top view of a one-part spring element according to a third embodiment; and 
       FIG. 3E  shows a cross section through the third embodiment of the one-part spring element. 
   

   DETAILED DESCRIPTION 
     FIG. 1  shows a diagrammatic basic illustration of an embodiment of the apparatus according to the invention in which two lever devices  12 ,  20  connected in series are provided. The first lever device has a first essentially plate-shaped transmission element  14  which is arranged perpendicularly with respect to the deflection direction L of an actuator  10  (of which only a plate is illustrated). The first transmission element  14  has a first bearing region  34  which lies on a surface of a guide plate  24  which is inserted in a circular recess of a second housing portion  28 . Furthermore, the first transmission element  14  has a second bearing region  36  which is assigned to the actuator  10 . A third bearing region  38  of the first transmission element  14  is assigned to a second transmission element  22  which is explained later. The first transmission element  14  has a (slightly) convex surface, the shape of which can be defined, for example, by grinding. The second bearing region  36  is in this case formed by the highest region. The underside of the first transmission element  14  has a recess which allows a relative movement between the first transmission element  14  and the guide plate  24 . The position in the image plane perpendicular to the deflection direction L of the actuator  10  is defined by a first spring element  16  and a second spring element  18  which are illustrated in the prestressed state. Between a first housing portion  26  and the second housing portion  28  are provided sealing surfaces  30 ,  32  which seal off the actuator space with respect to other regions of the apparatus. The first housing portion  26  and the second housing portion  28  can be brought to bear, for example, by means of the tightening of a fastening nut, for example in the form of a union nut. Before the first housing portion  26  and the second housing portion  28  come to bear against one another at the sealing surfaces  30 ,  32 , the first spring element  16  and the second spring element  18  project beyond the sealing surfaces  30  and  32  respectively. The first spring element  16  and the second spring element  18  are thus prestressed when the first housing portion  26  and the second housing portion  28  are moved toward one another. By means of the first and the second spring element  16 ,  18 , the guide plate  24  is prestressed against a surface of the housing portion  28 . Since the prestressing forces reduce the sealing forces, the prestressing forces must fulfill high accuracy requirements. The spring elements  16 ,  18  are therefore formed in such a way that they have a flat spring characteristic curve in relation to the generated force. The first spring element  16  and the second spring element  18  do not necessarily have to be formed in two pieces, but embodiments may also be considered in which the portions  16 ,  18  illustrated are formed by a one-piece element having a recess through which the first transmission element  14  extends. The one-piece design is illustrated in  FIG. 3D  as a third spring element  55 . 
   The second lever device  20  has a second transmission element  22  which may be designed at least essentially structurally identically to the first transmission element  14 . This second transmission element  22  has a fourth bearing region  40  which lies on a surface of the second housing portion  28  which forms an abutment for the second transmission element  22 . The second transmission element  22  has, furthermore, a fifth bearing region  42  which is provided in the highest region of the convex surface of the second transmission element  22 . A sixth bearing region  44  is assigned to an actuating member  46  to be actuated. The guide plate  24  is arranged partially above the bore in which the actuating member  46  is guided. The guide plate  24  serves preferably as a stop for the actuating member  46 . In order to ensure the clearance required for a relative movement between the second transmission element  22  and the second housing portion  28 , a recess is provided on the underside of the second transmission element  22 . Recesses or gradations are likewise provided in the second housing portion  28  in order to allow the respective relative movements. The second transmission element  22  is introduced into the guide plate  24  and is positioned by the guide plate  24  with respect to a plane which is oriented perpendicularly with respect to the direction of movement of the actuating member  46 . 
   Both the first spring element  16  and the second spring element  18  are essentially L-shaped in the prestressed state, a V-shaped portion  50  being provided in each case in the long leg of the L. The V-shaped portion  50  of the second spring element  18  can be supported on the second transmission element  22  (see also  FIG. 3A ) or on the correspondingly designed guide plate  24  (see also  FIG. 3B ), while the V-shaped portion of the first spring element  16  is supported on a guide plate  24 , lying on the second housing portion  28 , for the second transmission element  22 . Preferably, however, a spacing is formed between the V-shaped portion  50  and the second transmission element  22 , in order to ensure a free moveability of the second transmission element  22 . The forces exerted respectively on the guide plate  24  and on the second transmission element  22  by the V-shaped portions of the first spring element  16  and of the second spring element  18  are determined by the spring characteristics of the spring elements  16 ,  18 . This also applies similarly to the one-part version. 
   The first transmission element  14  has a first (short) lever arm A 1  and a second (long) lever arm B 1 . The second transmission element  22  similarly has a first (short) lever arm A 2  and a second (long) lever arm B 2 . A downwardly directed deflection of the actuator  10  is transmitted to the actuating member  46  by means of the construction illustrated, in that, first, the third bearing region  38  of the first transmission element  14  is deflected according to the ratio of A 1  and B 1 . The third bearing region  38  of the first transmission element  14  in this case acts on the fifth bearing region  42  of the second transmission element  22  and deflects the second transmission element  22 . The sixth bearing region  44  of the second transmission element  22  thereby acts on the actuating member  46  and deflects the latter as a function of the amount of deflection of the actuator  10  and of the lengths of the lever arms A 1 , B 1 , A 2  and B 2 . The two-stage lever device illustrated allows a high lever action, without a large amount of construction space being taken up. Furthermore, a high rigidity of the transmission elements  14 ,  22  can be achieved as a result of their relatively short lever arms. If appropriate, of course, even more than two lever stages may be provided, if this is necessary. In the embodiment illustrated, the actuator center axis m and the actuating member center axis M coincide, this being desirable in many instances. The center axes m and M in this case run through the second bearing region  36  and the sixth bearing region  44 . A preferred step-up ratio between a deflection of the actuator  10  and a deflection of the actuating member  46  amounts approximately to 1:5. An example of the dimensions of the respective lever arms is A 1 =A 2 =2.4 mm and B 1 =B 2 =3.6 mm. 
   When the first housing portion  26  and the second housing portion  28  are being joined together, the first spring element  16  and the second spring element  18  are prestressed or positioned in such a way that they guide or support the first transmission element  14  in the desired way, specifically without or with only slight play, with the result that a defined position or a stroke step-up with a narrow tolerance is ensured. 
     FIGS. 2A to 2C  illustrate diagrammatically the equilibria of forces for the first transmission element  14 , the first spring element  16  and the second spring element  18 . Forces corresponding to one another, but oriented in opposite directions are identified in each case by an apostrophe. The first spring element  16  exerts a first force F 1  on the first transmission element  14 , the first force F 1  being oriented approximately perpendicularly with respect to the deflection direction L of the actuator  10 . The second spring element  18  exerts on the first transmission element  14  a second force F 2  which corresponds in amount to the force F 1 , but is oriented in the opposite direction. Furthermore, the first spring element  16  exerts with its V-shaped portion  50  a fifth force F 5  on the guide plate  24  which is provided for the second transmission element  22 . It is preferred, in this case, that the fifth force F 5  exerted on the guide plate  24  is determined by the spring characteristic of the first spring element  16 . The V-shaped portion  50  of the second spring element  18  similarly exerts a sixth force F 6  on the guide plate  24  and/or on the second transmission element  22 . 
   The first spring element  16  is held in an equilibrium of forces by means of a prestressing force F 3 , the force F 3  comprising a force component F 3   y  which runs approximately parallel to the deflection direction L of the actuator  10 , and a force component F 3   x  which runs approximately perpendicularly with respect to the deflection direction L of the actuator  10 . 
   The second spring element  18  is similarly held in an equilibrium of forces by means of a prestressing force F 4 . The prestressing force F 4  likewise has a force component F 4   y  running approximately parallel to the deflection direction L of the actuator  10  and a force component F 4   x  running perpendicularly with respect to the deflection direction L of the actuator  10 . The force components F 3   y  and F 4   y  in this case correspond in amount to the forces F 5 ′ and F 6 ′. Depending on the application, the exertion of the first and of the second force F 1 , F 2  may even be dispensed with and only the guide plate  24  be prestressed by means of the fifth and the sixth force F 5 , F 6  on the second housing portion  28 . This prevents the guide plate  24  from being lifted off from the second housing portion. 
     FIG. 3A  shows a top view of the spring elements of  FIGS. 1 and 2B  and  2 C according to a first embodiment, and  FIG. 3B  shows a top view of the spring elements of  FIGS. 1 and 2B  and  2 C according to a second embodiment. 
   Both in the embodiment according to  FIG. 3A  and in the embodiment according to  FIG. 3B , the first spring element  16  and the second spring element  18  are fastened to an essentially annular carrier or, as is preferred, are formed in one piece with the latter. It may be gathered particularly clearly from the illustrations according to  FIGS. 3A and 3B  how the first spring element  16  and the second spring element  18  guide or support the first transmission element  14 . 
   In the embodiment according to  FIG. 3A , the second spring element  18  has a comparatively small width b 1  which makes it possible for the first spring element  16  to be supported on the second transmission element  22  (see  FIG. 1 ). 
   In the embodiment according to  FIG. 3B , the second spring element  18  has, in contrast to this, a comparatively large width b 2  which makes it possible for the second spring element  18  to be supported not on the second transmission element  22 , but, instead, on a guide plate, for example on the guide plate  24  of  FIG. 1 . 
     FIG. 3C  shows a diagrammatic top view of the circular guide plate  24  which has a guide recess  51  in which the second transmission element  22  is introduced and oriented in position with respect to the actuating member  46  and to the first transmission element  14  with narrow play. The guide recess  51  is adapted essentially to the outer contour of the second transmission element  22  and the position of the second transmission element  22  is thereby defined with slight play. Preferably, the guide recess  51  has two part recesses  52 ,  53  projecting laterally beyond the contour of the second transmission element  22 . The part recesses  52 ,  53  are formed symmetrically and opposite one another on two longitudinal sides of the guide recess  51 . Via the part recesses  52 ,  53 , the second transmission element  22  can be grasped laterally by means of pliers and lifted out of the guide recess  51 , for example for exchange. The bearing region of a third embodiment of a one-part spring element  55 , which is illustrated diagrammatically in  FIG. 3D , is arranged, as a broken circular line  54 , on the guide plate  24 . 
     FIG. 3D  shows a third spring element  55 , in the form of a circular disk, which constitutes a one-part version of the first and of the second spring element  16 ,  18  and serves for guiding the first transmission element  14  and for prestressing the guide plate  24 . The third spring element  55  has a guide orifice  56  in which the first transmission element  14  is introduced and oriented in position. The transmission element  14  is introduced into the guide orifice  56  with play in all directions. Preferably, the guide orifice  56  has the outer contour of the first transmission element  14 , although two part recesses  52 ,  53  arranged at the side edges of the guide orifice  56  may be formed opposite one another, which make it easier to demount the first transmission element  14 . The third spring element  55  has a slightly upwardly inclined circular edge region  57 . The edge region  57  serves for bearing against the first housing portion  26 . Furthermore, the third spring element  56  has a V-shaped portion  50  which runs circularly around the center of the third spring element  55  and is provided for bearing on the guide plate  24 . The third spring element  55  is, for example, stamped out of a spring steel sheet and shaped. 
   Preferably, the edge region  57  has recesses  58 . The recesses  58  are of preferably semicircular design and are arranged uniformly around the outer circumference of the edge region  57 . The recesses  58  serve, in the event of a desired spring rigidity of the third spring element  55  which is dependent on the material thickness of the third spring element  55 , for exerting on the guide plate  24 , via the V-shaped portion  50 , a defined prestressing force which is independent of the material thickness. The recesses  58  may also be designed in other shapes. 
     FIG. 3E  shows a diagrammatic cross section through the third spring element  55 . 
   The features of the invention which are disclosed in the above description, in the drawings and in the claims may be essential, both individually and in any desired combination, for the implementation of the invention.