Abstract:
Disclosed is a valve comprising a valve member ( 72 ) that is guided so as to be movable in the direction of the longitudinal axis ( 73 ) thereof, extends into a valve pressure chamber ( 77 ), and is provided with a sealing surface ( 81 ) on a face which runs perpendicular to the longitudinal axis ( 73 ) thereof inside the valve pressure chamber ( 77 ). Said sealing surface ( 81 ) of the valve member ( 72 ) cooperates with a valve seat ( 79 ) that runs perpendicular to the longitudinal axis ( 73 ) thereof so as to at least largely close an opening ( 78 ) which is surrounded by the valve seat ( 79 ) relative to the valve pressure chamber ( 77 ). A connection ( 64 ) to a low-pressure area lies immediately next to said opening ( 78 ). The inventive valve member ( 72 ) is also provided with a peg ( 83 ) which extends into the connection ( 64 ) and by means of which liquid that flows out of the valve pressure chamber ( 77 ) when the sealing surface ( 81 ) of the valve member ( 72 ) is lifted from the valve seat ( 79 ) is directed in such a way that said liquid applies at least nearly no resulting force onto the valve member ( 72 ) in the direction of the longitudinal axis ( 73 ) thereof.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
   This application is a 35 USC 371 application of PCT/DE2004/001744 filed on Aug. 4, 2004. 
   BACKGROUND OF THE INVENTION 
   1. Field of the Invention 
   The present invention is based on a valve for controlling a connection in a high-pressure fluid system, in particular in a fuel injection apparatus for an internal combustion engine. 
   2. Description of the Prior Art 
   A valve of the type with which this invention is concerned, known from EP 0 840 003 A, serves to control a connection in a fuel injection apparatus for an internal combustion engine and has a valve member that is guided so that it can slide in the direction of its longitudinal axis, protrudes into a valve pressure chamber, and, in the valve pressure chamber, has a sealing surface at an end extending transversely in relation to its longitudinal axis. The sealing surface of the valve member cooperates with a valve seat extending transversely in relation to its longitudinal axis in order to close an opening encompassed by the valve seat in relation to the pressure chamber. In this case, high pressure prevails in the valve pressure chamber and the opening is adjoined by a duct leading to a low-pressure region; the valve member controls the connection of the valve pressure chamber to the low-pressure region, thus controlling the pressure in the valve pressure chamber. When the valve is open, i.e. when its sealing surface is lifted away from the valve seat, fuel flows out of the valve pressure chamber into the low-pressure region. The outgoing fuel generates forces acting on the valve member in the direction of its longitudinal axis that can cause the valve member to move uncontrollably in the direction of its longitudinal axis. This can make it impossible to precisely control the fuel injection, chiefly the injected fuel quantity, or can even result in a complete functional failure of the valve and therefore of the fuel injection apparatus. In addition, the high flow velocity of the fuel flowing out of the valve pressure chamber into the low-pressure region and the lack of optimal flow guidance in the known valve can lead to cavitation and therefore damage to the valve member and/or the valve seat. 
   SUMMARY AND ADVANTAGES OF THE INVENTION 
   The valve according to the present invention has the advantage over the prior art that the operability of the valve is assured since the fuel flowing out of valve pressure chamber subjects the valve member to substantially no forces or only slight ones. 
   Advantageous embodiments and modifications of the valve according to the present invention are disclosed. One embodiment permits a simple design of the pin for achieving the desired action, while permits an at least approximately cavitation-free fluid flow along the valve member and along the valve seat. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     A number of exemplary embodiments of the present invention are described more fully herein below, with reference to the drawings, in which: 
       FIG. 1  shows a simplified longitudinal section through a fuel injection apparatus for an internal combustion engine, which is equipped with a valve, 
       FIG. 2  shows an enlarged longitudinal section through the valve according to a first exemplary embodiment of the invention, 
       FIG. 3  shows an embodiment of the valve that is modified in relation to the first exemplary embodiment, 
       FIG. 4  shows a longitudinal section through the valve according to a second exemplary embodiment, 
       FIG. 5  shows the valve according to the second exemplary embodiment, with a fluid flow, and 
       FIG. 6  shows an embodiment of the valve that is modified in relation to the second exemplary embodiment. 
   

   DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     FIG. 1  shows a fuel injection apparatus for an internal combustion engine of a motor vehicle. The internal combustion engine is preferably an autoignition internal combustion engine. The fuel injection apparatus is embodied, for example, in the form of a so-called unit injector and, for each cylinder of the engine, has a respective high-pressure fuel pump  10  and a fuel injection valve  12  connected to it that constitute an integrated structural unit. Alternatively, the fuel injection apparatus can also be embodied in the form of a so-called unit pump system in which the high-pressure fuel pump and the fuel injection valve of each cylinder are separate from each other and are connected to each other via a line. Furthermore, the fuel injection apparatus can also be embodied in the form of an accumulator injection system in which a high-pressure pump delivers fuel into an accumulator that is connected to the at least one injector in which a controlled valve is situated, which is embodied in the form of the valve  70  described below. The valve  70  described below can also be used in an accumulator injection system in which a pressure booster is provided, which is preferably close to the injector or integrated into the injector; the valve  70  is provided to control the pressure booster. The high-pressure fuel pump  10  has a pump body  14  with a cylinder bore  16  in which a pump piston  18  is guided in a sealed fashion and a cam  20  of a camshaft of the internal combustion engine at least indirectly drives this pump piston  18  into a stroke motion counter to the force of a return spring  19 . The pump piston  18  delimits a pump working chamber  22  in the cylinder bore  16  in which fuel is compressed at high pressure during the delivery stroke of the pump piston  18 . The pump working chamber  22  is supplied with fuel from a fuel tank  24  of the motor vehicle. 
   Connected to the pump body  14 , the fuel injection valve  12  has a valve body  26  that can be comprised of multiple parts, in which an injection valve member  28  is guided so that it can slide longitudinally in a bore  30 . The valve body  26  has at least one, preferably several injection openings  32  in its end region oriented toward the combustion chamber of the cylinder of the internal combustion engine. The end region of the injection valve member  28  oriented toward the combustion chamber has a for example approximately conical sealing surface  34 , which cooperates with a valve seat  36  that is embodied in the end region of the valve body  26  oriented toward the combustion chamber; the injection openings  32  lead from this valve seat  36  or branch off downstream of it. In the valve body  26 , between the injection valve member  28  and the bore  30 , toward the valve seat  36 , there is an annular chamber  38 , which, in its end region oriented away from the valve seat  36 , transitions by means of a radial expansion of the bore  30  into a pressure chamber  40  encompassing the injection valve member  28 . At the level of the pressure chamber  40 , the injection valve member  28  has a pressure shoulder  42  formed by a cross-sectional constriction. A prestressed closing spring  44  engages the end of the injection valve member  28  oriented away from the combustion chamber and presses the injection valve member  28  toward the valve seat  36 . The closing spring  44  is situated in a spring chamber  46  of the valve body  26  adjoining the bore  30 . 
   At its end oriented away from the bore  30 , the spring chamber  46  is adjoined in the valve body  26  by another bore  48  in which a control piston  50  connected to the injection valve member  28  is guided in a sealed fashion. The bore  48  constitutes a control pressure chamber  52  that is delimited by the control piston  50 , which functions as a moving wall. The control piston  50  is supported on the valve member  28  by means of a piston rod  51  that is smaller in diameter than, and can be connected to, the injection valve member  28 . The control piston  50  can be embodied of one piece with the injection valve member  28 , but for ease of assembly, is preferably embodied as a separate part that is attached to the injection valve member  28 . 
   According to  FIG. 1 , a duct  60  leads from the pump working chamber  22  through the pump body  14  and the valve body  26  to the pressure chamber  40  of the fuel injection valve  12 . A duct  62  leads from the duct  60  or the pump working chamber  22  to the control pressure chamber  52 . The control pressure chamber  52  can also be connected to a duct  64  that constitutes a connection to a discharge chamber, which function can be fulfilled at least indirectly by the fuel tank  24  or another region in which a low pressure prevails. A connection  66  controlled by a first electrically actuated control valve  68  leads from the duct  60  or the pump working chamber  22  to a discharge chamber. The fuel tank  24  or another low-pressure region can at least indirectly serve as the discharge chamber. The control valve  68  can be embodied in the form of a 2/2-way valve, as depicted in  FIG. 1 . An actuator  69  that can, for example, be an electromagnet switches the control valve  68  between its two switched positions, counter to the force of a return spring. 
   A second electrically actuated control valve  70  is provided to control the pressure in the control pressure chamber  52 . The second control valve  70  is embodied in the form of a 3/2-way valve that can be switched between two switched positions. In a first switched position, the control valve  70  connects the control pressure chamber  52  to the pump working chamber  22  and disconnects it from the discharge chamber  24 ; in a second switched position, the control valve  70  disconnects the control pressure chamber  52  from the pump working chamber  22  and connects it to the discharge chamber  24 . The connection  62  of the control pressure chamber  52  to the pump working chamber  22  contains a throttle restriction  63 , and the connection  64  of the control pressure chamber  52  to the discharge chamber  24  contains a throttle restriction  65 . The throttle restriction  63  can be situated in the connection  62  upstream of the control valve  70  or, as shown in  FIG. 1 , can be situated in the connection  62  downstream of the control valve  70 . The control valve  70  has an actuator  71  that can be an electromagnet, a piezoelectric actuator, or a magnetostrictive actuator and can switch the control valve  70  between its two switched positions counter to the force of a return spring. An electronic control unit  67  triggers the two control valves  68 ,  70 . 
   The second control valve  70  will be explained in greater detail below in conjunction with  FIG. 2 . The control valve  70  has a valve member  72  that is guided by means of a shaft  74  so that it can slide in the direction of its longitudinal axis  73  and, with an end region  75  whose diameter is enlarged in relation to the shaft  74 , protrudes into a valve pressure chamber  77 . On the one hand, the connection  62  to the pump working chamber  22  feeds into the valve pressure chamber  77  and on the other hand, the connection  64  to the discharge chamber  24  feeds from it. The connection  62  in this case extends in the form of annular gap between the shaft  74  and a bore  76  encompassing it. The bore  76  is smaller in diameter than the valve pressure chamber  77 . The connection  64 , which is embodied in the form of a duct or a bore, connects to the valve pressure chamber  77  by means of an opening  78  that is encompassed by a surface  79 , which constitutes a valve seat and extends transversely, preferably at least approximately perpendicularly, in relation to the longitudinal axis  73  of the valve member  72 . Toward the valve seat  79 , the valve member  72  has an at least approximately cylindrical extension  80  whose end surface constitutes a sealing surface  81  that extends transversely, preferably at least approximately perpendicularly, in relation to the longitudinal axis  73  of the valve member  72 . The extension  80  has a smaller diameter than the end region  75  of the valve member  72 , but the diameter of the extension  80  is greater than that of the opening  78 . 
   As depicted in  FIG. 2 , from the outer edge of the valve member  72 , the sealing surface  81  is inclined as it extends radially inward so that the distance between it and the valve seat  79  increases in the direction of the longitudinal axis  73  of the valve member  72 . This provides the outer edge of the sealing surface  81  with a narrow sealing edge with which the sealing surface  81  contacts the valve seat  79 . The valve member  72  has a pin  83 , which protrudes into the bore  64  adjoining the opening  78  and is preferably integrally formed onto the valve member  72 . As shown in  FIG. 2 , the diameter of the bore  64  can be enlarged after the opening  78 . The pin  83  is embodied such that when the control valve  70  is open, the pin deflects fuel flowing out of the valve pressure chamber  77  in such a way that this outgoing fuel exerts at least essentially no resulting force or only a slight resulting force on the valve member  72  in the direction of the longitudinal axis  73 . The pin  83  extends in the direction of the longitudinal axis  73  of the valve member  72  until the level of its sealing surface  81 . The transition from the inner edge of the sealing surface  81  to the pin  83  extends in a rounded fashion, as shown in  FIG. 2 . The fuel that initially flows out of the valve pressure chamber  77  along the sealing surface  81  in an approximately radial inward direction is consequently deflected by the pin  83  in such a way that it then flows into the bore  64  approximately in the direction of the longitudinal axis  73  of the valve member  72 . The pin  83  consequently initially deflects the fuel flow by approximately 90°. At its end protruding into the bore  64 , the pin  83  has an enlarged part  84  so that the fuel flow is deflected again there; this enlarged part  84  extends away from the valve member  72  at an angle γ in relation to the longitudinal axis  73  of the valve member  72 . The angle γ can be between greater than 0° and approximately 90° or can also be greater than 90°. Between its enlarged part  84  and the sealing surface  81 , the pin  83  can have a circumferential annular groove  85  whose side surfaces pointing in the direction of the longitudinal axis  73  of the valve member  72  deflect the fuel flow. Due to the multiple deflection of the fuel flow along the side surfaces of the annular groove  85 , the forces that the deflection produces on the valve member  72  in the direction of its longitudinal axis  73  at least approximately balance out so that on the whole, the fuel flow exerts at least approximately no force or only a slight force on the valve member  72  in the direction of the longitudinal axis  73 . The transitions from the side surfaces of the annular groove  85  to the bottom of the annular groove  85  and to the circumference of the pin  83  are each rounded in order to minimize flow losses. 
   The transition from the bore  76  into the valve pressure chamber  77  is provided with a conical transition surface  87  that constitutes a second valve seat. At the transition from the end region  75  to the shaft  74 , the valve member  72  is provided with a second, conical sealing surface  88  that cooperates with the valve seat  87  to control the connection  62 . In the second switched position of the control valve  70 , the second sealing surface  88  of the valve member  72  rests against the second sealing seat  87 , thus closing the connection  62  to the pump working chamber  22 . In the first switched position of the control valve  70 , the sealing surface  88  of the valve member  72  is spaced apart from the second valve seat  87 , thus opening the connection  62  to the pump working chamber  22 . In the first switched position of the control valve  70 , the sealing surface  81  of the valve member  72  rests against the valve seat  79 . 
   It is also possible for the actuator  71  to move the valve member  72  into a third switched position in which it is placed between its two switched positions explained above. The valve member  72  thus permits the valve pressure chamber  77  to be connected to the low-pressure region with a low flow cross section via which fuel is only able to flow out of the valve pressure chamber  77  in a throttled fashion. When the valve member  72  is in its third switched position, the pressure buildup in the control pressure chamber  52  is influenced in such a way that a higher pressure prevails in the control pressure chamber  52  than when the valve member  72  is in its first switched position, but a lower pressure prevails than when the valve member  72  is in its second switched position. The control valve  70  here is embodied in the form of a 3/3-way valve. 
     FIG. 3  shows a modified embodiment of the control valve  70  in which the conical valve seat  81  and the conical sealing surface  88  of the valve member  72  have been omitted. Instead, the valve member  72  is embodied in the form of a slide valve member for controlling the connection  62 . In order to close the connection  62 , the end region  75  of the valve member  72  here can plunge into the bore  76  in a sealed fashion. If the end region  75  of the valve member  72  has left the bore  76  and is positioned in the valve pressure chamber  77 , then the connection  62  is open. 
     FIG. 4  shows the control valve  70  according to a second exemplary embodiment in which the design is essentially the same as in the first exemplary embodiment, but the design of the sealing surface  81  has been modified. The pin  83  of the valve member  72  is embodied in the same form as in the first exemplary embodiment. The sealing surface  81  is embodied so that in an outer region  181  starting from its outer edge, the sealing surface  81  approaches the valve seat  79  as it extends radially inward. The region  181  of the sealing surface  81  here is inclined at an angle α that is preferably at least approximately 5° in relation to a radial plane of the longitudinal axis  73  of the valve member  72 . The region  181  of the sealing surface  81  has a radial span  11  that is preferably approximately 0.3 mm when a diameter of the valve member  72  is approximately 2.5 mm. In a second region  281  adjoining the first region  181 , the sealing surface  81  is embodied so that it recedes from the valve seat  79  as it extends radially inward. The second region  281  of the sealing surface  81  is inclined at an angle β, which is preferably at least approximately 2°, in relation to the radial plane. The second region  281  of the sealing surface  81  has a radial span  12  that is preferably approximately 0.6 mm. This embodiment of the sealing surface  81  provides it with a flow inlet region in its first region  181 —in which the fuel flowing out of the valve pressure chamber  77  is conveyed into the smallest flow cross section between the sealing surface  81  and the valve seat  79 —and provides it with a flow outlet region in its second region  281 —in which the fuel is conveyed out of the smallest flow cross section. As in the first exemplary embodiment, the valve seat  79  is embodied as at least approximately planar and lies in a radial plane in relation to the longitudinal axis  73  of the valve member  72 . The transition from the outer circumference of the extension  80  of the valve member  72  to the first region  181  of the sealing surface  81  is preferably rounded with a radius R, as shown in  FIG. 4 . 
     FIG. 5  shows the improved flow path with the valve member  72  according to the second exemplary embodiment. Whereas with the use of the valve member  72  according to the first exemplary embodiment, flow separations occur at the entry of the flow into the narrowest flow cross section between the sealing surface  81  and the valve seat  79 , with the use of the valve member  72  according to the second exemplary embodiment, these flow separations either do not occur at all or at least occur only to a limited degree. This reduces flow losses and achieves a cavitation-free flow. 
     FIG. 6  shows the control valve  70  according to an embodiment that has been modified in relation to the second exemplary embodiment. In this case, the sealing surface  81  on the valve member is embodied as at least approximately planar and lies in a radial plane in relation to the longitudinal axis  73  of the valve member  72 . The valve seat  79  is embodied in such a way that in an outer region  179  starting from its outer edge, the valve seat  79  approaches the sealing surface  81  as it extends radially inward. The region  179  of the valve seat  79  is inclined at an angle α, which is preferably at least approximately 5°, in relation to a radial plane of the longitudinal axis  73  of the valve member  72 . Starting from the outer edge of the sealing surface  81  of the valve member, the region  179  of the valve seat  79  has a radial span  11  that is preferably approximately 0.3 mm when a diameter d of the valve member  72  is approximately 2.5 mm. In a second region  279  adjoining the first region  179 , the valve seat  79  is embodied so that it recedes from the sealing surface  81  as it extends radially inward. The second region  279  of the valve seat  79  is inclined at an angle β, which is preferably at least approximately 2°, in relation to the radial plane. The second region  279  of the valve seat  79  has a radial span  12  that is preferably approximately 0.6 mm. This design, which is the reverse of the second exemplary embodiment, achieves the same advantages with regard to an optimized flow guidance as the second exemplary embodiment 
   The function of the fuel injection apparatus will be explained below. During the intake stroke of the pump piston  18 , it is supplied with fuel from the fuel tank  24 . During the delivery stroke of the pump piston  18 , the fuel injection begins with a preinjection in which the control unit  67  closes the first control valve  68  so that the pump working chamber  22  is disconnected from the discharge chamber  24 . The control unit  67  also brings a second control valve  70  into its second switched position so that the control pressure chamber  52  is connected to the discharge chamber  24  and disconnected from the pump working chamber  22 . In this case, high pressure is unable to build up in the control pressure chamber  52 . If the pressure in the pump working chamber  22  and therefore in the pressure chamber  40  of the fuel injection valve  12  is so great that the compressive force it exerts on the injection valve member  28  by means of the pressure shoulder  42  is greater than the sum of the force of the closing spring  44  and the compressive force that the residual pressure in the control pressure chamber  52  exerts on the control piston  50 , then the injection valve member  28  moves in the opening direction  29 , thus unblocking the at least one injection opening  32 . 
   In order to terminate the preinjection occurring in this manner, the control unit brings the second control valve  70  into its first switched position so that the control pressure chamber  52  is disconnected from the discharge chamber  24  and connected to the pump working chamber  22 . The first control valve  68  remains in its closed position. As a result, high pressure builds up in the control pressure chamber  52  and in the pump working chamber  22  so that a powerful compressive force acts on the control piston  50  in the closing direction and the injection valve member  28  is moved into its closed position. 
   For a subsequent main injection, the control unit  67  brings the second control valve  70  into its second switched position so that the control pressure chamber  52  is connected to the discharge chamber  24  and disconnected from the pump working chamber  22 . The fuel injection valve  12  then opens as a result of the reduced compressive force acting on the control piston  50  and the injection valve member  28  moves into its open position. 
   In order to terminate the main injection, the control unit  67  brings the second control valve  70  into its first switched position so that the control pressure chamber  52  is disconnected from the discharge chamber  24  and connected to the pump working chamber  22 ; as a result, high pressure builds up in the control pressure chamber  52  and the force exerted on the control piston  50  closes the fuel injection valve  12 . After the main injection, a secondary injection can also be executed for which the second control valve  70  is brought into its second switched position. In order to terminate the secondary injection, the second control valve  70  is brought back into its first switched position and/or the first control valve  68  is opened. 
   A control valve  70  embodied in the manner described above can also be used to control a connection in other fuel injection apparatuses or high pressure fluid systems. The control valve  70  can also be embodied in the form of a 2/2-way valve, a 2/3-way valve, or a 3/3-way valve. 
   The foregoing relates to preferred exemplary embodiments of the invention, it being understood that other variants and embodiments thereof are possible within the spirit and scope of the invention, the latter being defined by the appended claims.