Abstract:
Disclosed is a fuel conveying device including a valve housing in which a pressure release valve and a non-return valve are arranged parallel to one another, the pressure release valve having a first inlet, which downstream of a valve seat opens into a valve chamber in which a valve body is movably arranged and which is in fluid connection with a second inlet for the non-return valve via a first outlet. The device improves the control response of the pressure release valve by providing the first outlet at the periphery of the valve chamber and in the axial direction with respect to a valve axis such that when the pressure release valve is open the flow from the valve chamber into the second inlet is a substantially radial flow.

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This application is a 35 USC 371 application of PCT/EP 2006/065347 filed on Aug. 16, 2006. 
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The invention is directed to an improved fuel conveying device of the type used, for example, for supplying fuel to an internal combustion engine. 
     2. Description of the Prior Art 
     A fuel conveying device known from DE 195 27 134 A1 is equipped with a valve housing in which a pressure relief valve and a check valve are situated in parallel with each other; the pressure relief valve has a first inlet that, downstream of a valve seat, opens into a valve chamber in which a valve member is movably arranged and which, via a first outlet, is flow connected to a second inlet for the check valve. It is disadvantageous that the first outlet is situated in the valve chamber in a way that produces an axial outflow from the valve chamber of the pressure relief valve. The axial outflow exerts only a comparatively slight impulse force on the valve member, which therefore executes only a comparatively small opening stroke for a given volumetric flow. This results in a control response that is less than optimal. 
     SUMMARY AND ADVANTAGES OF THE INVENTION 
     The fuel conveying device according to the present invention has the advantage over the prior art that it improves the regulating behavior of the pressure relief valve in a simple way in that the first outlet is provided at the periphery of the valve chamber and is arranged in the axial direction such that when the pressure relief valve is open, an essentially radial outflow occurs from the valve chamber into the second inlet. 
     Advantageous modifications and improvements of the device are disclosed. It is particularly advantageous if the pressure relief valve and the check valve are arranged offset from each other in the axial direction so that the first outlet of the pressure relief valve feeds into the second inlet of the check valve in the radial direction. This achieves a radial outflow into the second inlet of the check valve. 
     It is also advantageous if the valve housing has a first recess for insertion of the pressure relief valve and a second recess that constitutes the second inlet for the check valve since this embodiment is particularly inexpensive to manufacture. The first recess and second recess are separated from each other by a wall. 
     It is particularly advantageous if the valve housing has two cylindrical sections, with one of the recesses provided in each section, since this embodiment is particularly space-saving. 
     It is also advantageous if the pressure relief valve has a separate housing on which the valve seat is embodied and in which the valve chamber with the valve member is provided since this simplifies the valve housing and makes it less expensive to manufacture. 
     It is also advantageous if the housing of the pressure relief valve is situated directly on the fuel conveying device and is attached to it. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       An exemplary embodiment of the invention is explained in greater detail herein below, with reference to the drawings, in which: 
         FIG. 1  is a schematic depiction of a conventional fuel conveying device, 
         FIG. 2  is a simplified sectional view of a valve housing according to the invention, equipped with a check valve and a parallel-connected pressure relief valve, and 
         FIG. 3  is a top view of the valve housing. 
     
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT 
       FIG. 1  is a schematic depiction of a fuel conveying device suitable to convey fuel, although the device is expressly also able to convey other fluids. 
     The device has a delivery unit  1  that draws fuel at least indirectly from a tank  2  and conveys it at an elevated pressure via a pressure line  3  to an internal combustion engine  4 , for example by supplying it to a fuel distributor  5 . The fuel distributor  5  is flow connected to injection valves  6  that inject the fuel into a combustion chamber, not shown, of the internal combustion engine  4 . 
     The delivery unit  1  is situated, for example, in the tank  2  and is provided, for example, inside a storage receptacle  9  therein. The deliver unit  1  draws fuel from this storage receptacle  9 , for example via a preliminary filter  10 , and delivers it to the internal combustion engine  4  via the pressure line  3 . The preliminary filter  10  protects the device downstream of the filter  10  from coarse dirt particles contained in the fuel. A check valve  11 , for example, is situated in the pressure line  3  to prevent fuel downstream of the check valve  11  from flowing back upstream of the check valve  11 . In addition, a main filter  12  that filters out fine dirt particles from the fuel is situated, for example, in the pressure line  3  downstream of the check valve  11 . Downstream of the delivery unit  1  and upstream of the check valve  11 , a drive line  13  branches off from the pressure line  3  and leads at least indirectly back into the storage receptacle  9 . The volumetric flow of the drive line  13  drives a so-called suction jet pump  16 , for example, which conveys fuel from the tank  2  into the storage receptacle  9 . The for example cup-shaped storage receptacle  9  stores enough fuel to assure the delivery unit  1  of being able to supply fuel to the internal combustion engine  4  even during cornering and the accompanying sloshing movements of the fuel in the tank  2 . 
     The suction jet pump  16  must be designed so that the storage receptacle  9  remains filled regardless of the level of fuel in the tank  2  and does not run dry. As is known, the suction jet pump  20  has a throttle element, for example a nozzle  17 , via which the fuel of the drive line  13  travels into a suction chamber  18  flow connected to the tank  2 . The motive jet coming from the nozzle  17  and traveling into the suction chamber  18  entrains fuel from the suction chamber  18  so that the fuel of the motive jet and the entrained fuel travel together in a known fashion into the storage receptacle  9  via a mixing conduit  19 . 
     Downstream of the check valve  11  and, for example, downstream of the main filter  12 , a return line  22  that contains a pressure relief valve  23  branches off from the pressure line  3  and leads back into the pressure line  3  upstream of the check valve  11 . 
     According to the invention, the check valve  11  and the pressure relief valve  23  are accommodated in a combined valve housing  24 . 
       FIG. 2  shows a valve housing according to the invention, equipped with a check valve and a parallel-connected pressure relief valve. 
     In the device according to  FIG. 2 , parts that remain the same or function in the same fashion as those in the device according to  FIG. 1  have been labeled with the same reference numerals. 
     The valve housing  24  has a first inlet  25 . 1  and first outlet  26 . 1  for the pressure relief valve  23  and a second inlet  25 . 2  and second outlet  26 . 2  for the check valve  11 . The first outlet  26 . 1  of the pressure relief valve  23  feeds directly into the second inlet  25 . 2  of the check valve  11 . 
     The valve housing  24  has two separate, for example cup-shaped, recesses  27 . 1 ,  27 . 2  that are separated from each other by a wall  29 . A first recess  27 . 1  accommodates the pressure relief valve  23  and a second recess  27 . 2  constitutes the second inlet  25 . 2  for the check valve  11 . The second recess  27 . 2  of the valve housing  24  can be slid onto an outlet fitting  28  of the delivery unit  1 , thus tightly sealing the flow connection between the outlet fitting  28  of the delivery unit  1  and the valve housing  24 . In this way, the valve housing  24  is situated directly on the delivery unit  1 . A mount  34  situated on the valve housing  24  attaches the valve housing  24  to the delivery unit  1  in a form-locked and/or non-positive and/or integrally joined fashion. For example, the mount is attached to an electrical plug  41  of the delivery unit in a form-locked and/or non-positive fashion. 
     The recesses  27 . 1 ,  27 . 2  are provided, for example, on two cylindrical housing sections of the valve housing  24 , with the first recess  27 . 1  being provided in a first cylindrical section  24 . 1  and the second recess  27 . 2  being provided in a second cylindrical section  24 . 2 . The two cylindrical sections  24 . 1 ,  24 . 2  of the valve housing  24  are integrally joined to each other. The first cylindrical section  24 . 1  protrudes beyond the second cylindrical section  24 . 2  in its longitudinal direction. The first inlet  25 . 1  is situated at an end of the first cylindrical section  24 . 1  and the second inlet  25 . 2  is situated at an end of the second cylindrical section  24 . 2  oriented away from the first inlet  25 . 1 . 
     The first recess  27 . 1  is closed by means of a cover  33  that has a shoulder  44 , for example, protruding into the first recess  27 . 1 . In this way, the pressure relief valve  23  in the first recess  27 . 1  is tightly sealed in relation to the atmosphere. 
     At an end of the second cylindrical section  24 . 2  oriented away from the second inlet  25 . 2 , there is a fitting  30  in which the check valve  11  is provided. The second inlet  25 . 2  feeds via a connecting conduit  31  into an additional valve chamber  45  of the check valve  11 , which valve chamber  45  is provided inside the fitting  30 . An additional valve member  46  is movably arranged in the additional valve chamber  45  and cooperates with all additional valve seat  47 . 
     The pressure relief valve  23  contained in the first recess  27 . 1  has a valve member  36  that cooperates with the valve seat  35  and is situated so that it can move in the axial direction with respect to a valve axis  38 . A valve spring  39  presses the valve member  36  toward the valve seat  35 . The valve seat  35  is embodied, for example, in the form of a flat seat and cooperates with a flat end of the for example cylindrical valve member  36 . For example, the valve seat  35  is embodied in the form of a raised annular surface on an end wall  40  of the valve chamber  37 . 
     For example, the pressure relief valve  23  has its own separate housing  42  on which the valve seat  35  is embodied and in which the valve chamber  37 , the valve member  36 , and valve spring  39  are provided. 
     According to present invention, the first outlet  26 . 1  of the pressure relief valve  23  is provided at the periphery of the valve chamber  37  and is oriented in the radial direction with respect to the valve axis  38  so that when the pressure relief valve  23  is open, an essentially radial outflow is produced from the valve chamber  37  into the first outlet  25 . 1  and into the second inlet  25 . 2 . The first outlet  26 . 1  of the pressure relief valve  23  is situated close to the valve seat  35  in the axial direction with respect to the valve axis  38 , for example in the same axial position as it. For example, the first outlet  26 . 1  extends through a first opening  20  at the periphery of the housing  42  of the pressure relief valve  23  and through a second opening  21  in the wall  29  between the recesses  27 . 1 ,  27 . 2 . The first opening  20  and the second opening  21  are aligned with each other. The pressure relief valve  23  and the check valve  11  are offset from each other in the axial direction with respect to the valve axis  38  so that the first outlet  26 . 1  of the pressure relief valve  23  feeds into the second inlet  25 . 2  in the radial direction with respect to the valve axis  38 . 
     If the pressure in the return line  22  exceeds a value predetermined by the spring force of the valve spring  39 , then the valve member  36  lifts away from the valve seat  35 , thus opening the pressure relief valve  23 . After the pressure relief valve  23  opens, fuel flows through the axial first inlet  25 . 1 , into the valve chamber  37  in the axial direction through a gap produced between the valve seat  35  and the valve member  36 , and exits this valve chamber  37  in the radial direction via the first outlet  26 . 1 . The flat seat permits a particularly favorable outflow in the radial direction. 
     An impulse force due to the deflection of the fluid from the axial direction into the radial direction acts on the valve member  36 , causing it to move in the direction away from the valve seat  35 , counter to the spring force of the valve spring  39  until a force equilibrium with the spring force is achieved. The impulse force of the flow increases as the flow through the pressure relief valve  23  increases. The spring force of the valve spring  39  increases in linear fashion as the stroke of the valve member  36  increases. An influx through the first inlet  25 . 1  into the valve chamber  37  in the axial direction with an outflow from the valve chamber  37  in the radial direction according to the invention maximizes the impulse force that the fuel exerts on the valve member  36 . The prior art, with both the inflow and outflow oriented in the axial direction, however, results in a weaker impulse force acting on the valve member  36 . 
     The impulse force works in opposition to the spring force. Ideally, the impulse force, which increases with increasing flow, compensates for the spring force, which increases with the stroke movement of the valve member  36 . As a result, the regulating pressure is kept as independent of the flow as possible. 
     The greater the impulse force acting on the valve member  36 , the larger the opening stroke executed by the valve member  36  and therefore the lower the overall pressure loss of the pressure relief valve  23  for a given flow. 
     The overall pressure loss of the pressure relief valve  23  essentially results from the pressure loss in the gap between the valve seat  35  and the valve member  36 . The pressure loss at this gap decreases as the stroke of the valve member  36  increases. 
     In the prior art with the axial outflow, however, an additional pressure loss occurs with the axial flow around the valve member  36 . This additional pressure loss in the prior at increases as the flow increases. The additional pressure loss that occurs in the prior art does not occur in the pressure relief valve  23  according to the invention since instead of an axial flow around the valve member  36 , a radial outflow occurs. 
     The elimination of the additional pressure loss achieves a better regulating behavior of the pressure relief valve  23  in comparison to the prior art since the overall pressure loss changes less markedly when slight changes in the flow occur. In this way, the pressure in the return line  22  and the pressure line  3  are kept virtually constant. 
       FIG. 3  is a top view of the valve housing. 
     In the device according to  FIG. 3 , parts that remain the same or function in the same fashion as those in the device according to  FIG. 1  and  FIG. 2  have been labeled with the same reference numerals. 
     The foregoing relates to a preferred exemplary embodiment 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.