Abstract:
A valve for metering fluid under pressure includes: a valve housing which has an inlet opening and a metering opening as well as a valve seat enclosing the metering opening having an outwardly pointing seat surface; a valve needle carrying a closing head; a valve-closing spring acting on the valve needle and applying the closing head to the valve seat; and an electrical actuator, which applies a compressive force to the valve needle, lifting the closing head outwardly away from the valve seat. To prevent transverse forces on the valve needle, which can cause a deflection of the valve needle, a gimbal-mounted spring disk, which is pushed onto the valve needle, is used as the valve-closing spring.

Description:
BACKGROUND OF THE INVENTION 
       [0001]    1. Field of the Invention 
         [0002]    The present invention relates to a valve for metering fluid, the umbrella term “fluid” referring to a flowing medium, for both gases and liquids in accordance with fluid dynamics. 
         [0003]    2. Description of the Related Art 
         [0004]    In a known, so-called outward-opening injector (Published European patent application document EP 2 366 888 A1), the valve housing has a hollow cylindrical nozzle body including a valve seat surrounding the nozzle opening situated at one end, a housing pot having the nozzle body protruding centrally through its pot bottom into the housing pot, and a housing cap which seals the housing pot and has a cap jacket and cap bottom, an inlet connection for the fluid being situated in the cap jacket. Inside the housing pot, a solenoid coil of an electromagnet sits on the nozzle body. A ring plate made of a nonmagnetic material is connected to the magnet pot and the nozzle body in a fluid-tight manner in each case and, together with the pot bottom of the housing pot, encloses an encapsulated coil space in which the solenoid coil is situated and, together with the housing cap, encloses a fluid-filled valve space into which the nozzle body protrudes. A valve needle is guided axially displaceably in the nozzle body and carries a closing head cooperating with the valve seat on one end. There is an annular clearance between the valve needle and the cylinder wall of the nozzle body, through which the fluid flows from the valve space to the metering opening. A magnet armature of the electromagnet attached to the valve needle delimits the working air gap of the electromagnet with the end face of the nozzle body protruding out of the coil space. A valve-closing spring, designed as a disk spring, is supported between the magnet armature and the support ring, exerting on the magnet armature a force, which applies the closing head to the valve seat via the valve needle. A folded or corrugated bellows arrangement, having a folded or corrugated bellows connected tightly to the valve needle and the cap bottom and a calibration spring situated in the folded or corrugated bellows, extends between the end of the valve needle remote from the closing head and the cap bottom of the housing cap in the valve space. The calibration spring is supported on the needle end of the valve needle on the one hand and on an axially adjustable adjusting bolt in the cap bottom on the other hand. The calibration spring may be prestressed in the desired way by displacement of the adjusting bolt and acts upon the valve needle with a compressive force acting in the valve opening direction. The diameter of the valve seat and the hydraulic diameter of the folded or corrugated bellows are the same, so that the valve needle is pressure equalized for all fluid pressures, and the dynamic response of the valve is independent of the fluid pressure. 
       BRIEF SUMMARY OF THE INVENTION 
       [0005]    The valve according to the present invention has the advantage that the gimbal-mounted spring, unlike a helical compression spring or a disk spring, which is generally used as the valve-closing spring, for example, does not exert any transverse force on the thin, elongated valve needle, thereby reliably preventing any deflection of the valve needle. Therefore, the valve needle may be passed through components of the electrical actuator with only a small radial clearance, so that both the outside diameter of the valve and the length of the valve may be kept small in combination with the low total height of the spring disk. The valve needle has additional radial support from the gimbal-mounted spring disk, so that the number of sliding guides of the valve needle in the valve housing may be reduced. Tolerance-related skewed positions of the supports of the spring disk relative to the central axis of the valve needle are compensated by the gimbal mount. The overall manufacturing costs of the valve are reduced. 
         [0006]    According to one advantageous specific embodiment of the present invention, the spring disk is supported on the valve needle and on the valve housing and one of the two supports is designed as a gimbal mount. Due to the prestressing of the spring disk required to generate the valve-closing force, a frictional force occurs at the support, which is not formed by the gimbal mount, so that the valve needle has additional radial support, while radial oscillation of the valve needle is prevented. This may be further improved by the fact that the gimbal mount is formed on the radial shoulder present on the valve needle, and the spring disk is secured on its support on the radial shoulder, which is provided on the valve housing, in at least some points. 
         [0007]    According to one advantageous specific embodiment of the present invention, the valve housing has a valve tube, a hollow valve body on the inlet end, which is connected to the valve tube at its one end in a fluid-tight manner, and in which the inlet opening is formed, and has a hollow valve body on the metering end, which is connected to the valve tube in a fluid-tight manner at its other end, the metering opening and the valve seat being formed in this valve body and the valve needle being guided axially displaceably. The radial shoulder present on the valve housing is secured by a ring surface, pointing toward the inlet end of the valve body, of a support ring, which rests on the valve tube near the inlet end of the valve body, or alternatively, is integrally molded in one piece on the metering end of the valve body, and the radial shoulder present on the valve needle is formed by an end face, pointing toward the metering end of the valve body, of a support sleeve, which is secured to and rests on the valve needle near the inlet end of the valve body, or alternatively, near the metering end of the valve body. These structural measures permit cost-efficient manufacture and simple assembly of the valve with implementation of the gimbal mounting of the spring disk taking place at the same time. 
         [0008]    According to advantageous specific embodiments of the present invention, the outer annular jacket of the support ring secured on the valve tube is provided with axial grooves to maintain fluid flow from the inlet opening to the metering opening when the support sleeve is secured on the valve needle near the inlet end of the valve body, or alternatively, the ring surface of the support ring integrally molded on the metering end of the valve body and pointing toward the inlet end of the valve body is provided with radial grooves when the support sleeve is secured on the valve needle near the metering end of the valve body. 
         [0009]    According to one advantageous specific embodiment of the present invention, the sleeve secured on the valve needle near the inlet end of the valve body is integrally molded in one piece on an adapter, connecting the end of the valve needle, remote from the closing head, to an elastic hollow body, which is situated coaxially with the valve needle in the hollow valve body on the inlet end at a radial distance from the wall of the body. At the same time, the adapter seals the hollow body in a fluid-tight manner on the end face, while a valve-closing element inserted with a fluid-tight seal into the valve body on the inlet end contains the inlet opening and seals the other end face of the hollow body in a fluid-tight manner. Such an elastic hollow body, which is under a vacuum or is filled with gas having a low thermal expansion, causes a hydraulic pressure equalization on the valve needle, thereby compensating for the fluid pressure acting on the closing head in the valve opening direction. The closing force of the spring disk may therefore be kept lower. With a lower valve-closing force, the compressive force of the electrical actuator required to open the valve is reduced, so that an electrical actuator of a lower power and thus a more compact design may be used. Integration of the hollow body into the valve body on the inlet end, which is additionally molded to form a connecting piece insertable into a connecting cup of a fluid supply line, avoids enlarging the axial total height of the valve due to the hollow body. 
         [0010]    An electromagnet is advantageously used as the electrical actuator. However, the electrical actuator may also be a piezoelectric or magnetostrictive actuator of a known type, which has a central bore through which the valve needle passes. The fluid flow is preferably guided over a hollow valve needle section in the area of the piezoelectrical actuator to the metering opening. 
         [0011]    When using an electromagnet, the magnet armature is fixedly connected to the valve needle, a hollow cylindrical magnetic core being secured in the interior of the valve tube, the valve needle passing through the magnetic core, a magnetic pot being secured on the outside of the valve tube and a solenoid coil being accommodated in the magnetic pot, resting with its coil body on the valve tube. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0012]      FIG. 1  shows a longitudinal section through a valve for metering fluid. 
           [0013]      FIG. 2  shows a top view of a valve-closing spring in the valve according to  FIG. 1 . 
           [0014]      FIG. 3  shows a section along line III-III in  FIG. 2 . 
           [0015]      FIG. 4  shows an enlarged diagram of detail IV in  FIG. 1 . 
           [0016]      FIG. 5  shows the same diagram as in  FIG. 4  with one modification in the area of the valve-closing spring. 
           [0017]      FIG. 6  shows a longitudinal section through the valve according to another exemplary embodiment. 
           [0018]      FIG. 7  shows an enlarged diagram of detail VII in  FIG. 6 . 
           [0019]      FIG. 8  shows the same diagram as that in  FIG. 7  with one modification in the area of the valve-closing spring. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0020]    The valve shown in a sectional view in the drawing for metering of fluid under pressure is inserted into the combustion chamber of an internal combustion engine or into an intake channel leading to the combustion chamber of the internal combustion engine for injection of fuel. However, it may also be used as an injection valve for metering of gas volumes in gas engines. 
         [0021]    The valve has a valve housing  11  having an inlet opening  12  for supplying fluid and a metering opening  13  for metered spraying of fluid. Valve housing  11  is assembled from a valve tube  14 , a hollow valve body  15  on the metering end connected in a fluid-tight manner to valve tube  14  on its tube end and a hollow valve body  16  on the inlet end, also connected in a fluid-tight manner to valve tube  14  on its other end. The fluid-tight connection is established with the aid of an integral bond, for example, by peripheral welds  17 ,  18 . Metering opening  13  and a valve seat  19  surrounding metering opening  13  and having a seat surface pointing outward in the spray direction are formed at the end in valve body  15  on the metering end. Valve body  16  on the inlet end has inlet opening  12 . It is molded to form a connecting piece, which is inserted into a connecting cup  20 , indicated with dashed lines, of a so-called rail, i.e., a feeder line for the fluid, and is sealed there with the aid of a sealing ring  21 . The valve has a thin, elongated valve needle  22 , which is provided with a closing head  221  and is pressure equalized by an elastic hollow body  23 , which is exposed to the fluid pressure and is connected to valve needle  22  by an elastic hollow body on the end of valve needle  22  remote from the closing head. The term “pressure equalized” as used here means that the compressive force of the fluid acting on closing head  221  in the opening direction is compensated approximately by the tensile force created by hollow body  23  on valve needle  22  under the influence of the fluid pressure. Elastic hollow body  23  is aligned coaxially with valve needle  22  and is accommodated in valve body  16  on the inlet end. A valve-closing spring  24 , which places closing head  221  on valve seat  19 , engages on valve needle  22 . An electrical actuator  25 , which engages on the end of valve needle  22  remotely from the closing head, is used for lifting the closing head  221  of valve needle  22  from valve seat  19  against the closing force of valve-closing spring  24 . The electrical actuator  25  is, for example, an electromagnet which has in a known way a magnet armature  26  including axial channels  37  for the fluid passage connected to valve needle  22 , a magnet armature  26  enclosing a working air gap  27 , a hollow cylindrical magnetic core  31  forming a so-called internal pole, a magnet coil  29  and a magnet pot  30  enclosing magnet coil  29 . Magnet pot  30  is secured externally on valve tube  14  using a pot section of a smaller diameter and is coupled to valve tube  14  via a ferromagnetic return path yoke  36  located at its pot opening. Internal pole or magnetic core  31  is secured internally on valve tube  14  and surrounds a needle section of valve needle  22 . Valve needle  22  is guided axially displaceably by two sliding sections  222 ,  223  in valve body  16  on the metering end. Sliding sections  222 ,  223  are provided with axial grooves  32  for the passage of fluid. 
         [0022]    Elastic hollow body  23 , which is aligned coaxially with valve needle  22  and is preferably designed as a metallic folded or corrugated bellows  35 , is hermetically sealed at one end by an adapter  33  and at the other end by a closure element  34  and is filled with a gas having a low thermal expansion or a vacuum. Adapter  33  is secured on the end of valve needle  22  remotely from the closing head, and closure element  34  is inserted in a fluid-tight manner into valve body  16  on the inlet end. Inlet opening  12  in the form of an axial through-bore is introduced into closure element  34 . The tight connection of adapter  33  and closure element  34  to metallic folded or corrugated bellows  35  is again accomplished with the aid of an integral bond. Likewise the connection of adapter  33  to valve needle  22  and closure element  34  to valve body  16  on the inlet end are established with the aid of an integral bond. Folded or corrugated bellows  35  has a hydraulic diameter D 2 , which is at least approximately equal to diameter D 1  of valve seat  19 . Hydraulic diameter D 2  is understood here to be a diameter on which the fluid under pressure acts over the entire axial length of elastic hollow body  23  or folded or corrugated bellows  35 . The pressure of the fluid on the folded or corrugated bellows  35  is converted by folded or corrugated bellows  35  into a tensile force acting on the end of valve needle  22  remote from the closing head, this tensile force being applied to closing head  221  against valve seat  19 . 
         [0023]    Valve-closing spring  24  is designed as a gimbal-mounted spring disk  40  pushed onto the valve needle, which is supported on valve needle  22  and on valve housing  11 , one of the two supports being designed as a gimbal mount. Spring disk  40  is shown in a top view in  FIG. 2  and in a sectional view in  FIG. 3 . The support of spring disk  40  on the valve needle end rests on a radial shoulder present on valve needle  22  and the support of spring disk  40  on the valve housing end rests on a radial shoulder present on valve housing  11 . The gimbal mount is formed by a spherical zone having sphere radius r, which is integrally molded on the shoulder surface of the radial shoulder on valve needle  22  pointing toward the metering end of valve body  15  having metering opening  13 , or is alternatively molded in the shoulder surface of the radial shoulder on valve housing  11 , this shoulder surface pointing toward valve body  16  on the inlet end having inlet opening  12 . 
         [0024]    In the exemplary embodiment of the valve according to  FIGS. 1 through 5 , the radial shoulder present on valve housing  11  is formed by a ring surface of a support ring  41  pointing toward the inlet end of valve body  16  having inlet opening  12 , and the support shoulder present on valve needle  22  is formed by an end face of a support sleeve  42  pointing toward the metering end of valve body  15  having metering opening  13 , this end face being situated near the inlet end of valve body  16  on valve needle  22 . Support sleeve  42  is integrally molded in one piece on the adapter  33  connecting the folded or corrugated bellows  35  to valve needle  22  ( FIGS. 4 and 5 ). Support ring  41  is secured on valve tube  14  by welding near the inlet end of valve body  16  above magnet armature  26 , for example, and has axial grooves  43  for the passage of fluid in its annular jacket on the outside of valve tube  14 . 
         [0025]    In the exemplary embodiment of the valve according to  FIGS. 1 through 4 , the gimbal mount is formed on support sleeve  42  by integral molding of a spherical zone having sphere radius r on the lower end face of support sleeve  42  pointing toward the metering end of valve body  15 . Spring disk  40  rests with its spring edge under prestress on the ring surface of support ring  41  pointing toward the inlet end of valve body  16 . Due to the prestress, a frictional force occurs between spring disk  40  and support ring  41 . Valve needle  22  is additionally supported radially by this frictional force and prevents radial oscillation of valve needle  22 . This may be further improved by the fact that—as will not be discussed further here—spring disk  40  is secured in at least some spots in its support on support ring  41 , which may be achieved by spot welds, for example. In this structural embodiment, sliding guide  222  on valve needle  22  may be omitted. The prestress of spring disk  40  is adjusted by appropriate displacement of valve needle  22  in adapter  33  before adapter  33  having integrally molded support sleeve  42  is connected to valve needle  22  by integral bonding. In  FIG. 4 , the integral bond between valve needle  22  and adapter  33  is made visible by weld  44 , and the integral bond of adapter  33  to folded or corrugated bellows  35  is made visible by peripheral weld  45 . 
         [0026]    The modification shown in  FIG. 5  in the arrangement of valve-closing spring  24  differs from the arrangement shown in  FIG. 4  in that the gimbal mount and the support of spring disk  40  on support ring  41  and support sleeve  42  are switched, i.e., the gimbal mount is on support ring  41  and the support of spring disk  40  is on support sleeve  42 . The spherical zone having sphere radius r is integrally molded into the ring surface of support ring  41  pointing toward the inlet end of valve body  16  in which spring disk  40  rests at its outer edge area, while the inner edge area of spring disk  40  rests on the end face of support sleeve  42  pointing toward valve body  15  on the metering end. 
         [0027]    The exemplary embodiment of the valve shown in  FIGS. 6 through 8  differs from the exemplary embodiment described previously only in the displacement of the arrangement of valve-closing spring  24  away from valve body  16  on the inlet end above magnet armature  26  toward the metering end of valve body  15  beneath magnetic core  31 .  FIG. 6  otherwise corresponds to  FIG. 1 , so that the same parts are labeled with the same reference numerals. The radial shoulder present on valve housing  11  is again formed by the ring surface of a support ring  41 ′ pointing toward the inlet end of valve body  16  having inlet opening  12 , and the radial shoulder present on valve needle  22  being formed by the end face of a support sleeve  42 ′ pointing toward the metering end of valve body  15  having metering opening  13 . In contrast with  FIGS. 1 through 5 , support ring  41 ′ is formed in one piece on metering end of valve body  15  and has radial grooves  46  for the passage of fluid in its end face, while support sleeve  42 ′ is secured integrally bonded on valve needle  22  near the metering end of valve body  15 . The integral bond is implemented with the aid of a peripheral weld  47 . 
         [0028]    In the exemplary embodiment in  FIGS. 6 and 7 , the gimbal mount is provided on support sleeve  42 ′, and the support of spring disk  40  is provided on support ring  41 ′. To form the gimbal mount, the spherical zone having sphere radius r is integrally molded on the lower end face of support sleeve  42 ′ pointing toward the metering end of valve body  15 . The prestress of spring disk  40 , with which it rests on support ring  41 ′, is adjusted by corresponding positioning of support sleeve  42 ′ relative to support ring  41 ′ before support sleeve  42 ′ is welded to valve needle  22 . 
         [0029]    The modification shown in  FIG. 8  in the arrangement of spring disk  40  differs from that shown in  FIG. 7  by switching the gimbal mount and the support for spring disk  40 . 
         [0030]    The gimbal mount is formed on support ring  41 ′ and the support of spring disk  40  is provided on support sleeve  42 ′. For this purpose, the spherical zone having sphere radius r is molded into the ring surface of support ring  41 ′ pointing toward the inlet end of valve body  16 , spring disk  40  with its outer edge being enclosed in the spherical zone in a form-fitting manner, while the inner spring edge area of spring disk  40  rests on the end face of support sleeve  42 ′ pointing toward the metering end of valve body  15  under prestress. This prestress is adjusted by the same method as that described previously.