Abstract:
An injection valve for injecting fuel into a combustion chamber includes: a housing having at least one spray discharge orifice on a discharge side; a solenoid coil; a magnet armature linearly movable by the solenoid coil; a valve needle for opening and closing the spray discharge orifice, which valve needle projects through the magnet armature and is linearly movable along a longitudinal axis, the magnet armature being linearly movable in relation to the valve needle between a first stop and a second stop, the second stop being formed by a stop element having a stop face and a counter element having a counter face situated opposite the stop face, the stop element having an elastic design so that an angle between the longitudinal axis and the stop face is changed when the counter face strikes the stop face.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to an injection valve for injecting a medium, e.g., for injecting fuel into a combustion chamber, which injection process may be developed as a port injection or as a direct injection. 
     2. Description of the Related Art 
     The related art includes known injection valves for the injection of Otto fuel. They have a valve needle which is moved against a closing spring by an actuator, e.g., an electromagnet or a piezo actuator, in such a way that a desired fuel quantity is selectively introduced directly into the combustion chamber. In the case at hand, an injection valve is examined in which the magnetic armature is decoupled from the valve needle. When the injection valve is opened, the magnetic armature is meant to rapidly detach from the lower stop (second stop) on the valve needle, to rapidly overcome the armature free travel, and to quickly open the valve when striking the upper (first) stop. If the energization of the valve is stopped, then the valve needle closes again. Once the valve needle seals the valve seat again, the magnetic armature continues its movement until it strikes the lower stop. The armature bounces off the lower stop multiple times before reattaining its idle position. The time until the magnet armature is reset to the idle position again is decisive for the ability of the valve to deliver injections in rapid succession and with high accuracy. A squish gap is usually developed at the lower stop, i.e., between the magnetic armature and the corresponding stop sleeve on the valve needle. The medium to be injected is squeezed into this squish gap, so that the magnetic armature is reset to the idle position in a damped and rapid manner during the closing. However, by damping the movement during the opening, the squish gap prevents a rapid opening. As a compromise, the squish gap must therefore be configured in such a way that the magnet armature opens the valve with sufficient speed and is reset to its idle position with sufficient speed as well. 
     BRIEF SUMMARY OF THE INVENTION 
     The injection valve of the present invention allows for better damping of the magnet armature and thus makes it possible to reset the magnet armature to its idle position more rapidly than previously possible after the injection valve is closed. At the same time, the damping during the opening of the injection valve is reduced in the present invention, so that the injection valve opens more rapidly. More specifically, the following advantages thus result in the opening of the injection valve: The magnet armature detaches from the valve needle more rapidly than previously, which increases the dynamic response of the valve and therefore improves the function. The required opening force is reduced, so that the current consumption of the injection valve, and thus the entire energy requirement of the vehicle, is lower. This lowers the consumption of the vehicle. The following advantages result in the closing of the injection valve: The movement of the magnet armature is damped to a greater extent than before. The magnet armature therefore reaches its idle position earlier than previously, so that injections are able to be delivered in rapid succession and with high repeat accuracy. The injection valve according to the present invention provides new injection strategies that make possible a combustion featuring lower pollutant emissions and lower consumption. The better damping in the closing of the injection valve reduces the noise that is created by the pulse transmission of the magnet armature to the valve needle. All of these advantages are achieved by an injection valve according to the present invention, which includes a housing having at least one spray-discharge orifice on a discharge side, a solenoid coil and a magnetic armature, which is linearly movable with the aid of the solenoid coil. In addition, the injection valve has a valve needle. This valve needle is used for the opening and closing of the at least one spray-discharge orifice. The valve needle extends along a longitudinal axis and is linearly movable. A through hole is developed in the magnet armature, in which the valve needle is situated. The magnet armature is linearly movable between a first and a second stop in relation to the valve needle. This creates a two-mass system. The first stop is formed on a side of the magnet armature facing away from the discharge. For example, the first stop is formed by a ring on the valve needle. The second stop is formed on a side of the magnet armature facing the discharge. According to the present invention, the second stop is formed by a stop element and a counter element. The stop element and the counter element strike each other at the second stop. The stop element has a stop face for this purpose. A counter face situated across from the stop face is developed on the counter element. The stop face and counter face strike each other at the second stop. The stop element has an elastic design, so that an angle between the longitudinal axis and stop face changes when the counter face and the stop face strike each other. In particular, the stop face is inclined toward the counter element prior to and following the contact between stop element and counter element. As soon as the counter element and stop element make contact with each other, the stop element is elastically deformed, so that the space between the stop face and counter face becomes smaller. Because of the elastic development of the stop element according to the present invention, it is possible that there is a change in the squish gap and the throttle flow between the stop face and counter face when the stop face and counter face move towards and away from each other. This enables a very precise adjustment of the damping in the opening and closing of the injection valve. 
     The stop element is preferably permanently connected to the valve needle. The counter element will then be situated on the magnet armature. The counter element in particular is an integral component of the magnet armature. In the most straight-forward case, the counter face is the side of the magnet armature that faces the stop face. In an alternative development, it is possible that the stop element is permanently connected to the magnet armature. The counter element will then be permanently joined to the valve needle. Decisive is that at least one of the opposing surfaces on the second stop has an elastic design. This at least one elastic surface is referred to as stop face within the scope of the present application. 
     The stop element or counter element is preferably integrated into the valve needle. As an alternative, the stop element or counter element is integrated into the magnet armature. 
     It is furthermore preferably provided that the angle between the longitudinal axis and stop face without contact between stop face and counter face is less than 90° at least regionally. The angle is defined on the side of the stop face that faces the counter face. This means that the angle of less than 90° defines that the stop face is inclined toward the counter face. It suffices if the stop face has this inclination at the corresponding angle only in certain places. When the counter face strikes the stop face, the stop face will be deformed, so that the angle becomes greater. 
     When lifting off from the stop face and counter face, i.e., during the opening of the injection valve, the stop element relaxes again, so that the angle becomes smaller again. Because of the development of the angle it is possible that the movement of the magnet armature is damped only by a throttle flow but no squish gap when the injection valve opens. As soon as the counter face and the stop face move slightly apart from each other, the stop element relaxes and the stop face thus inclines in the direction of the counter face. As a result, the stop face and counter face are no longer aligned in parallel with one another, and no squish gap is present. Only a throttle flow, i.e., the flow of the medium to be injected, which flows out of the region between stop face and counter face, dampens the opening movement of the magnet armature. 
     When the injection valve closes, the stop face and the counter face move toward each other. In so doing, the stop face is initially inclined in the direction of the counter face, so that a relatively large space filled with the medium is present between the stop face and counter face. The movement is initially dampened by a throttle flow, and as soon as the stop face and counter face make contact with each other, the stop face is deformed, so that the stop face aligns itself parallel to the counter face. This creates a squish gap for damping the movement of the magnet armature. The damping effect therefore increases as the clearance between stop face and counter face becomes smaller. 
     It is provided, in particular, that the angle without the contact between stop face and counter face amounts to maximally 89.99 degrees, preferably maximally 89.85 degrees. As already described earlier, this angle need not be provided across the entire stop face. 
     It is furthermore preferably provided that as a result of the striking contact between counter face and stop face, the angle is elastically deformed by at least 0.01 degrees, preferably at least by 0.15 degrees. In an especially preferred specific embodiment, the stop face is deformed until the stop face and counter face are in parallel alignment with each other. 
     It is furthermore advantageous that the stop face is subdivided into an inner section and an outer section. The inner section is closer to the longitudinal axis than the outer section. Especially preferably, the stop face is an annular surface around the valve needle. The inner section is an inner annular surface. The outer section is a further annular surface lying outside of the inner section. The angle without contact between stop face and counter face is larger at the outer section than at the inner section. In this context it is preferably provided that the stop face inclines more heavily in the direction of the counter face as the distance from the longitudinal axis increases. 
     Especially preferably, it is provided that the inner section without contact between stop face and counter face is developed parallel to the counter face. As an alternative, the inner section may be slightly inclined in the direction of the counter face or have a concave design. 
     On the stop element, a side facing away from the counter face is referred to as outer surface. This outer surface should also be formed appropriately, so that enough elasticity is available for the deformation of the stop face. As a consequence, the outer surface is preferably formed so that it inclines in the direction of the counter element or is at least regionally concave. As an alternative, the outer surface may regionally also lie parallel to the stop face. It is also decisive in this context that the stop element is as thin as possible, so that the stop face is able to deform elastically. 
     In order to ensure the elastic deformability of the stop element, and thus also of the stop face, grooves are preferably provided in the stop element. These grooves are especially preferably formed over the entire circumference of the longitudinal axis. 
     The first stop is preferably formed by a step or by a ring on the valve needle. 
     Exemplary embodiments of the present invention are described in detail below with reference to the accompanying drawing. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  shows an injection valve according to the present invention for all exemplary embodiments. 
         FIG. 2  shows a detail of an injection valve of the present invention, according to a first exemplary embodiment. 
         FIG. 3  shows a further detail of an injection valve of the present invention, according to the first exemplary embodiment. 
         FIGS. 4 through 7  show a movement sequence at the injection valve of the present invention, according to the first exemplary embodiment. 
         FIG. 8  shows the injection valve of the present invention, according to a second exemplary embodiment. 
         FIG. 9  shows the injection valve of the present invention, according to a third exemplary embodiment. 
         FIG. 10  shows the injection valve of the present invention, according to a fourth exemplary embodiment. 
         FIG. 11  shows the injection valve of the present invention, according to a fifth exemplary embodiment. 
         FIG. 12  shows the injection valve of the present invention, according to a sixth exemplary embodiment. 
         FIG. 13  shows the injection valve of the present invention, according to a seventh exemplary embodiment. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     In the following text, a first exemplary embodiment of injection valve  1  will be discussed with the aid of  FIGS. 1 through 7 . Identical components or functionally identical components are designated by identical reference symbols in all exemplary embodiments. 
       FIG. 1  illustrates the general structure of injection valve  1  for all the exemplary embodiments. Injection valve  1  includes a housing  2  having a spray discharge orifice  4  on a discharge side  3 . Housing  2  supports a solenoid coil  5 . A valve needle  6  including a ball  7  is disposed along a longitudinal axis  15  in the interior of housing  2 . Ball  7  together with housing  2  forms a valve seat for opening and closing spray orifice  4 . 
     In addition, a magnet armature  8 , which is connected to a spring cup  9 , is situated inside housing  2 . On a side of magnet armature  8  that faces away from the discharge is a ring  10 , which is fixedly secured on valve needle  6 . This ring  10  forms a first stop for magnet armature  8 . On a side of magnet armature  8  facing the discharge is a stop element  12 . This stop element  12  forms a second stop together with magnet armature  5 . 
     Both valve needle  6  and magnet armature  8  are linearly movable along longitudinal axis  15 . The movement of magnet armature  8  is delimited by the first and second stop. 
     A plurality of channels  16  for the medium to be injected are developed in magnet armature  8 . In addition or as an alternative, valve needle  6  may also have a hollow design. 
     Valve needle  6  is loaded in the direction of discharge side  3  by means of a first spring  11 . A second spring  13  between spring cup  9  and stop element  12  loads magnet armature  8 , likewise in the direction of discharge side  3 . 
     Magnet armature  8  is moved by energizing solenoid coil  5 . By way of the first and second stop, magnet armature  8  carries valve needle  6  along. The distance between the two stops defines an armature free travel  14 . 
       FIG. 2  shows a detail of injection valve  1  according to a first exemplary embodiment. It is obvious that stop element  12  is integrally formed with a sleeve  20 . Sleeve  20  is situated on valve needle  6  and permanently joined to valve needle  6 . Magnet armature  8  is simultaneously developed as so-called counter element  18 . 
     A surface on stop element  12  facing counter element  18  is referred to as stop face  17 . Situated across from stop face  17  is a counter face  19  on counter element  18 . A side on stop element  12  facing away from counter element  18  is referred to as outer surface  21 . The plotted angle α is defined between stop face  17  and longitudinal axis  15 . Angle α is measured on the side of stop face  17  facing counter element  18 . 
     Stop element  12 , and thus also stop face  17 , are elastically deformable. When counter element  18 , i.e., magnet armature  8 , strikes stop element  12 , stop element  12  is elastically deformed, so that angle α becomes larger. 
       FIG. 3  shows sleeve  20  and stop element  12  in detail. Sleeve  20  and stop element  12  have a through hole  28  that is coaxial with respect to longitudinal axis  15 . Valve needle  6  is situated in this through hole  28 . 
     A first height  25  extends parallel to longitudinal axis  15 , from the upper end of through hole  28  to the outer end of stop face  17 . The outer end of stop face  17  is referred to as peak  27 . A second height  26  designates the extension of stop element  12  parallel to longitudinal axis  15 . The elasticity of stop face  17  in the illustrated exemplary embodiment is achieved in that the two heights  25 ,  26  are greater than 0. 
       FIGS. 4 through 7  show a movement sequence during the opening and closing of the injection valve.  FIG. 4  shows the idle state, in which solenoid coil  5  is not energized and magnet armature  8  merely rests lightly on stop element  12 . Accordingly, stop face  17  is not deformed and stop face  17  is inclined toward counter face  19  at an angle α of less than 90 degrees. 
     In the following figures, reference numeral  29  denotes a throttle flow of the medium to be injected. The dashed illustration of stop element  12  shows the elastic deformation. 
     Because of the applied magnetic field at solenoid coil  5 , magnet armature  8  is pulled in the direction of the inner pole in  FIG. 5 , i.e., in the upward direction in the illustration. Valve needle  6  remains in the valve seat, until magnet armature  8  has overcome armature free travel  14  and carries valve needle  6  along via ring  10  (first stop). As long as a relative movement is present between magnet armature  8  and valve needle  6 , throttle flow  29  comes about between magnet armature  8  and valve needle  6 , i.e., between stop face  17  and counter face  18 . Throttle flow  29  between stop face  17  and counter face  19  decreases with rising clearance, so that the injection valve is able to open rapidly. In  FIG. 6 , the current at solenoid coil  5  is switched off, and the magnetic field decays. Valve needle  6  is in the seat, and magnet armature  8 , coming from the first stop on ring  10 , is able to continue its movement in the direction of the second stop on stop element  12 . Because of the relative movement between magnet armature  8  and valve needle  6 , a throttle flow  29  is once again created between stop face  17  and counter face  19 . Throttle flow  29  increases with decreasing clearance, so that the movement of magnet armature  8  is damped to a growing extent. When magnet armature  8  makes contact with stop element  12 , i.e., counter element  19  exerts pressure on stop face  17 , stop element  12  is elastically deformed by the push, and the damping volume situated between stop face  17  and counter face  19  turns into a squish gap. This state is illustrated in  FIG. 7 . The movement of magnet armature  8  is decelerated as a result. The elastic deformation of stop element  12  aligns stop face  17  in a coplanar manner in relation to counter face  19 , so that the damping of the magnet armature movement by the squish gap is maximized. 
       FIG. 8  shows a detail of injection valve  1  according to a second exemplary embodiment. In the second exemplary embodiment, stop face  17  is subdivided into an inner section  23  and an outer section  24 . Even without contact with counter face  19 , inner section  23  is disposed perpendicularly to longitudinal axis  15 , and thus also in parallel with counter face  19 . In outer section  24 , stop face  17  is inclined at angle α in the direction of counter face  19 . 
     Outer surface  21  is situated partially in parallel with counter face  19  and partially inclines toward counter face  19 . More specifically, outer surface  21  is inclined in the direction of the counter face roughly in the region of outer section  24 , so that sufficient elasticity of stop element  12  is provided there. 
       FIG. 9  shows a detail of injection valve  1  according to a third exemplary embodiment. In the third exemplary embodiment, stop face  17  is inclined in the direction of counter face  19  both in inner section  23  and in outer section  24 . However, the inclination toward outer section  24  is more pronounced, so that the greatest deformation of stop element  12  occurs there. 
       FIG. 10  shows a detail of injection valve  1  according to a fourth exemplary embodiment. In the fourth exemplary embodiment, stop face  17  is inclined in the direction of counter face  19  in inner section  23  and in outer section  24 , in the same way as in the third exemplary embodiment. From sleeve  20 , outer surface  21  is heavily inclined throughout in the direction of counter face  19 . This creates a very narrow stop element  12 , especially in the outer region, which is elastically deformable accordingly. 
       FIG. 11  shows a detail of injection valve  1  according to a fifth exemplary embodiment. In the fifth exemplary embodiment, stop face  17  is disposed parallel to counter face  19  across inner section  23 . Stop face  17  is concave along outer section  24 . Outer surface  21  of stop element  12  likewise has a concave design. This creates a relatively narrow stop element  12  having rounded transitions between the various inclinations, so that a dependable elasticity is ensured. Angle α is hereby defined by the tangent, is to the concave development of stop face  17  in outer section  24  and longitudinal axis  15 . 
       FIG. 12  shows a detail of injection valve  1  according to a sixth exemplary embodiment. In the sixth exemplary embodiment, a groove has been provided in outer surface  21  of stop element  12 . This groove  22  is developed peripherally about longitudinal axis  15 , in particular. Groove  22  weakens stop element  12  accordingly, so that the desired elasticity is provided. 
       FIG. 13  shows a portion of injection valve  1  according to a seventh exemplary embodiment. Seventh exemplary embodiment once again shows a groove  22  for adjusting the elasticity of stop element  12 . In the seventh exemplary embodiment, groove  22  is situated in an area of stop element  12  that extends in parallel with longitudinal axis  15 . This has the result that groove  22  comes very close to peak  27  and stop face  17 , so that not entire stop element  12  but only an upper portion is deformed in this exemplary embodiment. 
     The various exemplary embodiments show possible geometries of stop element  12 . In the exemplary embodiments, stop faces  17  are usually in the form of a wedge, since the wedge form is easy to measure and produce. The exemplary embodiments may naturally also be combined. For example, grooves  22  shown in  FIGS. 12 and 13  with the appropriate form depth and number in the other exemplary embodiments as well. Furthermore, an adaptation of outer surface  21  according to  FIGS. 9, 10 and 11  is possible in all exemplary embodiments. The different angles and concave developments of stop face  17  of the various exemplary embodiments can be combined with one another. In addition, all other concave and convex forms of stop element  12  are possible, as long as sufficient elasticity is ensured. Additional cross-sectional forms for groove  22  are triangles and ellipses, for example. Even more than one groove  22  per stop element  12  is possible in order to adapt the stiffness appropriately. The exemplary embodiments show rotationally symmetrical valve needles  6  that are not hollow. In the same way, it is possible to use the present invention with hollow and/or not rotationally symmetrical valve needles  6 . Even stop face  17  or counter face  19  need not have a rotationally symmetrical design. 
     All exemplary embodiments shown illustrate stop face  17  and counter element  19  in a form in which it is fixedly joined to valve needle  6 . Accordingly, magnet armature  6  in the exemplary embodiments is defined as counter element  18  having counter face  19 . In the same way, it is possible to develop an elastic stop element  12  which is permanently connected to magnet armature  6 . Correspondingly, counter element  18  would then be fixedly joined to valve needle  6 . In the simplest development, counter face  19  is a planar rigid surface. It is also possible for counter face  19  to have a certain inclination and elasticity.