Abstract:
A fuel injector for injecting pressure fuel in a combustion chamber of an internal combustion engine has an injector housing, an inlet connectable with a high pressure collecting chamber, a nozzle inlet line, a 2/2-way valve for opening and closing the nozzle inlet line, a control chamber in which a pressure change occurs, at least one first ball valve positioned at a side of the control chamber, at least one second ball valve positioned at a side of the inlet, and a guide element movable in the housing, the first and second ball valve being positioned opposite to one another and associated with the movable guide element.

Description:
BACKGROUND OF THE INVENTION 
     The present invention relates to a pressure-control injector for injecting fuel with a double valve. 
     The fuel injection systems commonly used for direct injection and internal combustion engines nowadays contain a high-pressure collecting chamber (common rail). In addition to a high pressure collecting chamber the injection system includes injectors which project into a combustion chamber of an internal combustion engine to be supplied with fuel. Upon injection the demand for the fuel quantity to be injected and the starter injection is exceptionally important and must take into consideration the ignition leg. Moreover, the injectors represent mechanically loaded components whose fatigued strength at favorable manufacturing costs must not fall below the service life of the internal combustion engine. 
     Reference numerals EP 0 657 642 A2 and DE 197 01 879 A1 each disclose a fuel injection device for combustion engines. More specifically, each of these documents describes a fuel injection device that includes a high pressure pump which is assigned to a high pressure accumulating chamber (common rail) that is to be filled with fuel. A high pressure accumulating chamber is connected via injection lines with injection valves projecting into the combustion chamber of the internal combustion engine. The opening or closing movements are controlled respectively by an electrically control valve. The control portion is formed as a 3/2 way valve, which is connected with the injection line or a release line to a high pressure channel opened to an injection opening of the injection valve. A hydraulic working chamber or a pressure release chamber fillable with high pressure fuel is provided on a control member of the control part. The working chamber is controllable for adjustment of the set position of the control member of a release channel. As the case may be, during a pause an injection a connection between the injection valve and the release chamber can be created. Both these devices have a considerable overall height. 
     SUMMARY OF THE INVENTION 
     Accordingly, it is an object of present invention to provide a pressure-control injector for injecting fuel with a double valve, which avoids the disadvantages of the prior art. 
     In contrast to the devices described above, the present invention provides a 3/2-way valve which has a very compact construction and can be produced in a cost effective manner due to the use of ball-shaped bodies. The ball-shaped bodies arranged as ball valves opposite to one another represent simple standard parts, which based on the geometry, allow an optimal pressure distribution of the surface to receive the pressure. In addition, the solution proposed in the present invention makes possible the production of a simply constructed 3/2 valve without the need for relative movements of a seat surface. 
     The positioning of the balls lying opposite to one another on and supported by a common guide, bring about a self-centering of the balls in their respective ball sockets in a simple manner. Another manufacturing advantage associated with the valve configuration is that the ball sockets lye freely on or on top of the faces of the guide, and by the respective pressure forces take care of the centering itself with reference to a center line of the injector. The ball sockets are composed of a soft metal or a soft metal alloy to facilitate a secure support and to ensure an optimal fitting to the ball surface geometry. Thus, with the configuration of the injector in accordance with the present invention adjusting plate is avoided in the life of the injector, and a centering of the ball sockets and the balls received therein relative to the guide and thereby to the line of symmetry of the injector is realized. The guide which has the ball sockets. 
     The guide which has the ball sockets on its upper and lower sides is provided with free spaces which permit a longitudinal flow of the pressurized fuel upon pressure release of the control chamber by regulation of a 2/2 valve. A pressure release of the nozzle chamber of the injection nozzle takes place through a pressure release of the nozzle inlet and the pressure chamber connected thereby via the ball valve on the control chamber side to which upon closing of the common rail the nozzle inlet line releases various oil. 
     With the use of a high pressure receiving chamber line which is angled at 90°, its connection to the injector body is lateral, and the height of the inventive injector is favorably affected or in other words minimized. 
     The novel features which are considered as characteristic for the present invention are set forth in particular in the appended claims. The invention itself, however, both as to its construction and its method of operation, together with additional objects and advantages thereof, will be best understood from the following description of specific embodiments when read in connection with the accompanying drawings. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a view showing a longitudinal cross-section through a housing of an injector with ball valves located opposite to one another and supported on a guide and ball sockets for receiving the ball valves, in accordance with the present invention. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     An injector for injecting a high pressure fuel in a combustion chamber of the internal combustion engine shown in FIG. 1 has an injector housing  2  with an inlet  5  coming from a high pressure collecting chamber open beneath a dividing seam  35 . For space saving purposes the inlet  3  from the high pressure collecting chamber is formed as a bore extending at an angle of 90°, so that inside the injector housing  2  beneath a guide  19  a hollow chamber  28  can be located in order to create an injector  1  with particularly compact dimensions. 
     A bore  4  is provided in the injector housing  2  and branches off from the inlet  3  to the high pressure collecting chamber. The bore  4  opens into a control chamber  6  via an inlet throttle  5 . These features make possible that in a control chamber  6  a constant and adequate control volume is maintained under high pressure. The control chamber  6  which actuates the vertical movement of the guide  19  is associated with a 2/2-way valve. The 2-2/way valve can be a hydraulic/mechanical regulating unit, a piezo actuator, or a magnetic valve, as is not specifically shown in FIG.  1 . 
     By means of this not shown element which makes possible the advantageous and short response and control time features which are even more important with high rotational speed of the internal combustion engine, a sealing body  8  is pressure-unloaded with a corresponding control. Thereby the sealing body  8  shown here as a ball slides up on its sealing seat  9  and releases an outlet throttle  10  which is located behind a release opening  11  provided above the control chamber  6 . The control chamber  6  is balanced by regulation of the 2/2-way valve  7 . 
     By balancing of the control chamber  6  a control chamber piston  12  located opposite to the release opening  11  descends into the control chamber  6 . The pole  17  of the ball valve  16  on the control chamber side which lies on a contact point  15  of the control chamber piston  12  moves upwardly and closes off the waste oil line  14  which branches transversely relative to the control chamber piston  12  in the injector housing  2 . The control chamber piston  12  is formed with a diameter which exceeds the valve diameter  25  on the ball  24  of the oppositely disposed ball valve  23 . 
     The ball valve  16  provided on the control chamber side as well as the ball valve  23  provided on the high pressure collecting chamber side are received in a hollow chamber provided in the injector housing  2 . The hollow chamber is partially filled by a guide  19 , wherein ball sockets  18  are provided at oppositely located faces of the guide. The ball sockets  18  are freely movable relative to the faces of the guide  18  and preferably composed of a soft, metallic material or a soft metallic alloy. In addition of the ball sockets  18 , a rounded portion  26  or  27  is formed, each of which corresponds to the ball  17  or  24  received in the ball sockets  18 . 
     Based on this construction of the ball sockets  18  composed of soft metal an exact fit of the radius of curvature of the outer surfaces of the balls  17  or  23  with the socket rounded portions  26 ,  27  in the respective ball socket  18  is realized. In connection with this, the construction of the ball sockets  18  enables the balls  17  or  24  to be sufficiently centered to the socket rounded portions  26 ,  27  of the ball sockets  18 . Furthermore, the selected configuration provides for a self-centering of the ball socket  18  in the balls  17  and  23  relative to the line of symmetry of the injector housing  2 . From a manufacturing point of view, the arrangement of the ball sockets on the faces of the guide  19  offers advantages, since the sufficient operational position of the guide is independent from a form-locking connection of the ball sockets  18  with the guide  19  during the operation of the inventive injector. 
     The guide  19  is provided near a guide area  34  with free surfaces or spaces  20 . The guide area  24  serves for guiding the guide  19  free from play in a vertical direction in the hollow chamber in the injector housing  2 . The free spaces  20  permit a longitudinal flow of the pressurized fuel along the free spaces  20  of the guide  19  and introduction of the pressurized fuel through the transverse bore in a longitudinal bore  22 , which represents the nozzle inlet to the nozzle chamber to the injection nozzle needle. The above-described longitudinal flow occurs upon pressure release of the control chamber  6  in the above described longitudinal flow occurs upon pressure release of the control chamber  6  in the above described manner, or in other words by controlling the actuator elements an opening of the oppositely located valves, of the high pressure receiving chamber  3 . 
     Due to the angled configuration of the inlet  3  to the ball valve  23  on the inlet side, a sealing spring  30  in the hollow chamber  28  can be positioned directly under the inlet  3  from the high pressure collecting chamber in the injection housing  2 . The sealing spring  30  in the hollow chamber  23  abuts against a disc-shape member  29  and lies with its opposite ends on a ball shaped pressure member  31 . An end of the pressure member  31  receives a pin  33  of the nozzle needle  32 , so that the sealing force of the sealing spring  30  on the nozzle needle  32  can be transferred, with the sealing spring  30  pressed in its sealing seat in the area of the injector opening. By regulating of the 2/2 control valves  7  and therefore the pressure release of the control chamber  6 , the control chamber piston  12  descends into the control chamber  6 . The ball  17  of the ball valve  16  on the control chamber side descends into its sealing seat in the injector housing  2  and closes the waste oil line  14 . At the same time the ball  24  of the ball valve  23  located on the lower surface of the guide  19  descends and opens the inlet from the high pressure accumulating chamber. High pressure fuel flows over the inlet  3  into the hollow chamber of the injector housing  2 , passes over the free space  20  of the guide  19  and enters into the nozzle inlet  22  through the transverse bore  21 . The nozzle inlet  22  drains into a nozzle chamber (not shown in FIG. 1 which surrounds the injector nozzle in front of its injector seat). Its position the waste oil line  14  opposite the high pressure is closed by the ball  17  when it descends into its seat in the injector housing  2 . 
     The ball  24  on the inlet side ball valve  23  is pressed with its valve diameter  25  into its seat in the injector housing upon closing of the inlet  3  from the high pressure collecting chamber. This is performed by an increase of the pressure in the control chamber  6  via the bore and the inlet throttle  5 . Since the diameter  13  of the control chamber piston  12  is larger than the valve diameter  25  of the ball valve  23 , a downward vertical movement of the guide  19  and the hollow chamber within the injector housing  2  occurs, so that the inlet  3  from the high pressure receiving chamber can be closed. At the same time, the ball  17  of the control chamber side ball valve  16  opens the waste oil line  14 . Thus, the nozzle inlet  22  and therefore the nozzle chamber of the injection nozzle can be released by the transverse bore  21  and the upper portion of the hollow chamber of the injector housing  2 , so that the pressure fuel can run back into the tank via the waste oil line  14 . 
     The main idea of the present invention therefore resides in two ball-shaped ball valves  16  and  23 , each located in a socket  18  of the surface of a guide  19 , wherein the valves self center opposite the seat in the injector housing  2 . This permits a simple manufacture of the component since the tolerances can be favorably chosen and since the self centering can be automatically adjusted, based on the prevailing pressure during operation in both areas of the hollow chamber within the injector housing  2  containing the guide  19 . Therefore this reason a seat surface need not be movable relative to the guide. In addition, the seat surface can be stationary in the injector housing  2  since with the selected geometry of the counter parts, that is the balls  17  and  23 , an adaptation to the final structural conditions of the seat surfaces of the injector housing  2  can be precisely determined. Thus, a seal seat without leakage can be achieved with a favorable selected tolerance in the injector housing  3 . 
     It will be understood that each of the elements described above, or two or more together, may also find a useful application in other types of constructions differing from the types described above. 
     While the invention has been illustrated and described as embodied in pressure-control injector for injecting fuel with a double valve, it is not intended to be limited to the details shown, since various modifications and structural changes may be made without departing in any way from the spirit of the present invention. 
     Without further analysis, the foregoing will so fully reveal the gist of the present invention that others can, by applying current knowledge, readily adapt it for various applications without omitting features that, from the standpoint of prior art, fairly constitute essential characteristics of the generic or specific aspects of this invention.