Patent Publication Number: US-6659424-B2

Title: Valve arrangement for pressure regulation of fuel supply in an internal combustion engine

Description:
FIELD OF THE INVENTION 
     The invention relates to a valve arrangement for the pressure regulation of the fuel supply in an internal combustion engine having at least one pressure regulating device and a shutoff device that can be actuated by an electromagnetic drive. 
     BACKGROUND 
     Valve arrangements are known for engines with direct fuel injection. Such engines require injection pressures of approximately 100 to 120 bars. This pressure is produced by high-pressure pumps, which are very sensitive to cavitation and therefore, the fuel that is introduced must be free of vapor bubbles. Under normal engine operation, a positive pressure of approximately 4 bars is sufficient to transport the fuel free of vapor bubbles from a delivery pump to the high-pressure pump. During engine startup, however, the pressure must be increased to approximately 7 bars in order to suppress the formation of vapor bubbles and to reliably establish the injection pressure when the engine is started without utilizing a mechanical high-pressure pump. The required increase in pressure to 7 bars is achieved by a shutoff device that can be activated electromagnetically and by a 4-bar pressure regulation device arranged in front of or behind the shutoff device. 
     Such a valve arrangement requires a very large structural space and is also very expensive due to the increased expenditure for its assembly. 
     SUMMARY OF THE INVENTION 
     An object of the present invention is to provide apparatus for overcoming the problems discussed above. 
     The object is achieved in that a housing is provided with at least one inlet connection and at least one outlet connection, which are in fluid communication by a connection channel, wherein the electromagnetic drive opens or closes the connection channel by means of an armature on a tappet with a closing element, and with at least one pressure spring element which acts directly or indirectly on the closing element in the closing direction. 
     In this way, a valve arrangement is obtained, which is simple and inexpensive to manufacture and also requires less structural space and a smaller expenditure for assembly. Both the pressure regulation of the fuel supply as well as the shutoff capability is assured by this single component. 
     In a first embodiment, magnetic force acts on the armature in the closing direction of the closing element, and, in addition, the pressure spring, which is supported on the housing, acts on the armature in the closing direction. This embodiment represents a so-called “current-free open” variant. That is, in the absence of electrical current a low pressure level of approximately 4 bars is established by means of the pressure spring. When electrical current is supplied, a magnetic force is applied to the tappet by means of the armature, which raises the pressure to a high-pressure level of approximately 7 bars including the pressure spring. 
     In a second embodiment, the magnetic force acts on the armature in opposition to the closing direction of the closing element and a first pressure spring acts on the armature in the closing direction, while a second pressure spring acts on the tappet in the closing direction. Both pressure springs are supported by the housing. In this way, a “current-free closed” variant of the valve arrangement is produced. The spring forces of the two pressure springs add up to approximately 7 bars when no current is supplied. When current is supplied, the magnetic force acts against the first pressure spring, so that only the second pressure spring with a pressure of approximately 4 bars acts on the tappet in the closing direction. 
     A particularly simple valve arrangement is then produced if the housing has two inlet connections and two outlet connections. The first inlet connection is connected to the delivery pump and the second inlet connection is connected to the return line from the high-pressure pump. The first outlet connection is connected to the admission line of the high-pressure pump and the second outlet connection is connected to the return line to the fuel tank. 
     The housing contains an armature core that can be adjustably moved in the housing and which supports the pressure spring such that the pressure applied by the armature can be adjusted in a simple manner. It is also particularly advantageous if the electromagnetic drive has a proportional magnet system, wherein the armature core has an elliptical outer contour. The armature core is thus not exactly round at the magnetic flux transmission site, so that minimum and maximum magnetic forces can be obtained by a 90° rotation of the core which in turn makes possible a force adjustment of the electromagnet drive. 
    
    
     BRIEF DESCRIPTION OF THE DRAWING 
     FIG. 1 is a schematic illustration of a conventional fuel flow system in an internal combustion engine, 
     FIG. 2 is a cross sectional view of a first embodiment of the valve arrangement according to the invention, 
     FIG. 3 is a cross sectional view of a second embodiment of the valve arrangement according to the invention. 
    
    
     DETAILED DESCRIPTION 
     FIG. 1 shows schematically a fuel flow circuit for an internal combustion engine in which a pressure regulation of the fuel delivery is obtained by a valve arrangement  1 . The fuel is transported from a fuel tank  2  by a delivery pump  3  to a high-pressure pump  4 , which introduces the fuel at a pressure of approximately 100 to 120 bars to a fuel distributor  5 . A pressure regulator  6 , which is arranged downstream of the distributor  5 , regulates the outlet fuel pressure to 4 bars. The fuel is then directly introduced into valve arrangement  1  or is introduced in conjunction with the fuel present in a bypass line  7 . In the conventional case, valve arrangement  1  comprises a pressure regulating valve  8  and a shutoff valve  9 . Fuel is led back into fuel tank  2  from shutoff valve  9 . 
     The fuel flow circuit functions as follows: 
     When the engine is started, shutoff valve  9  is closed, so that pressure regulating valve  8 , which opens at a pressure valve value of approximately 4 bars, is out of operation. Delivery pump  3  delivers fuel at a pressure of approximately 7 bars. A pressure regulator  10  is arranged in the fuel tank to open at a pressure of more than 7 bars. In this way, during the start-up phase, fuel is delivered free of vapor bubbles to high-pressure pump  4 , which produces injection pressures of approximately 100 to 120 bars and introduces the fuel to distributor  5 . During the normal operation phase, shutoff valve  9  is opened by means of an electromagnetic drive, so that a pressure of approximately 4 bars is produced in the fuel circuit by pressure regulation valve  8 . Fuel in front of high-pressure pump  4  or afer pressure regulation valve  6  can be returned to valve arrangement  1  and from there into fuel tank  2 . 
     FIG. 2 shows a first embodiment of the valve arrangement  1  according to the invention. The valve arrangement  1  has an inlet connection  11  and an outlet connection  12 , which are connected to one another by a connection channel  13 . The connection channel can be opened or closed by a closing element  14 . Closing element  14  is arranged on a tappet  15  which is actuated by an electromagnetic drive  16  to selectively open and close connection channel  13 . The tappet  15  travels in a guide bush  20 . 
     Electromagnetic drive  16  comprises a coil  17 , which cooperates with an electromagnetic yoke  18 . The coil  17  and yoke  18  are arranged in an injection-molded housing  19 . In addition, an armature  21  is mounted in a second guide bush  20  so that the armature  21  can be moved in a longitudinal direction. A pressure spring  22  acts on armature  21  in the closing direction of closing element  14 . Pressure spring  22  is supported on a core  23  which is supported in housing  19  for adjustable longitudinal and rotational movement. By adjusting the longitudinal position of the core  23  in the housing  19  the spring force can be adjusted. By making the outer contour of the core elliptical, when the core is turned by 90°, the magnetic force can be adjusted between maximum and minimum values on the armature. After the core is adjusted in its longitudinal and angular positions in the housing the core is secured by suitable means, such as, a bolt, clamp, screw or the like. The current supply of the electromagnetic drive is provided by a plug connection  24 . 
     The valve arrangement  1  in FIG. 2 serves as a current-off open embodiment and functions as follows: 
     In the operation phase of the engine, the electromagnetic drive  16  is not supplied with electrical current. Accordingly, magnetic force is not applied to armature  21  and valve arrangement  1  is in a current-off open state. Pressure spring  22  has a low pressure level of approximately 4 bars. Now, if a system pressure which is greater than 4 bars is reached in the fuel cycle circuit, closing element  14  opens against the action of pressure spring  22  and fuel can be returned to fuel tank  2 . In the current applied state, armature  21  is pressed against tappet  15  by the magnetic force and by the spring force. The magnetic force can be adjusted so that a pressure level of approximately 7 bars is reached. Valve arrangement  1  then only opens at a pressure level in the fuel circuit, which is higher than 7 bars. As has already been described the magnetic force is adjusted by rotating the armature core  23 . 
     FIG. 3 shows a cross section of a second embodiment of a valve arrangement  1 ′. The same elements with the same function have the same reference numerals. The valve arrangement  1 ′ has two inlet connections  25  and  26  and two outlet connections  27  and  28 . Valve arrangement  1 ′ is connected directly to delivery pump  3  by inlet connection  25 , and fuel is transported to high-pressure pump  4  by outlet connection  27 . The second inlet connection  26  is connected to pressure regulator  6  and brings excess fuel back into fuel tank  2  via outlet connection  28 . Connection channel  13  thus simultaneously takes on the function of bypass line  7  shown in FIG.  1 . 
     Valve arrangement  1 ′ operates in a “current-off closed” state, in contrast to valve arrangement  1  of FIG.  2 . That is, in the current-off state, the maximum pressure level of approximately 7 bars is achieved by the closing force which acts on closing element  14 . For this purpose, the valve arrangement  1 ′ has a pressure spring  29 , which acts on armature  21  in the closing direction and a second pressure spring  30 , which acts on tappet  15  in the closing direction. Both pressure springs  29  and  30  are supported on the housing and produce a combined maximum spring force, which corresponds to a pressure level of approximately 7 bars. In the engine startup phase, this valve arrangement  1 ′ is not supplied with electrical current so that fuel is transported at 7 bars to the high-pressure pump  4 . When the pressure level of 7 bars is exceeded, closing element  14  opens and thus opens bypass line  7  via the connection channel  13 , so that fuel can return to fuel tank  2 . In the operating phase of the internal combustion engine, valve arrangement  1 ′ is supplied with current and the magnetic fore moves armature  21  against pressure spring  29 , so that only pressure spring  30  still acts on tappet  15  at a pressure of 4 bars, so that the valve opens when a pressure exceeds 4 bars and fuel can be returned to fuel tank  2  through connection  28 . 
     Although the invention is disclosed with reference to particular embodiments thereof, it will become apparent to those skilled in the art that numerous modifications and variations can be made which will fall within the scope and spirit of the invention as defined by the attached claims.