Abstract:
A method for the continuous measuring of dynamic fluid consumption using a continuously-operating flow sensor with variable pressure drop wherein the pressure downstream of the flow sensor is adjusted to a constant value by a pressure regulator, and when the pressure downstream of the pressure regulator exceeds a certain level, recycling fluid back into the pressure regulator in an amount that corresponds to the volume causing the excess pressure.

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
       [0001]    This application is a continuation-in-part of application Ser. No. 10/804,234, filed Mar. 19, 2004, which claimed priority of Austrian application GM 198.2003, filed Mar. 21, 2003. All priorities are claimed. 
     
    
     BACKGROUND OF THE INVENTION 
       [0002]    1. Field of the Invention 
         [0003]    The invention relates to a method for continuous measuring of dynamic fluid consumption, particularly of fuel, by means of a continuously-operating flow sensor with variable pressure drop, preferably a mass flow sensor, whereby the pressure beyond the flow sensor is adjusted to a constant value by means of a pressure regulator. The invention addresses furthermore a pressure regulator having a housing, which contains an element biased by a changeable force acting against the pressure to be regulated whereby this element is coupled to a valve arrangement that is also arranged in the housing for the pressure build up of the fluid therein. The invention relates also to a device for continuous measuring of dynamic fluid consumption, particularly of fuel, comprising a tank, possibly a fuel conditioning system, and preferably a controllable pump, a continuously-operating flow sensor for the fluid, preferably a Coriolis sensor, and a initial-pressure regulator for the admission pressure between the flow sensor and the fluid consumer. 
         [0004]    2. The Prior Art 
         [0005]    Intermittently operating systems based on scales are known in the art for measuring consumption of fluids, especially in the application of fuel consumption of engines on test benches. They have the advantage of being open systems, namely they have the characteristic whereby fuel can be delivered from the measuring system and returned to the system at limited time-intervals and limited volume. The dispensed amount of fuel as well as the returned fuel amount are measured and taken into account in the consumption reading. Open systems are advantageous especially for modern injection systems since they force fuel back at the start of the engine during the pressure buildup, within limited volume into the fuel supply system—in case of motor vehicles this volume is drawn back to the vehicle&#39;s tank. Such scales have been shown to be of disadvantage in that they have to be always refilled and a continuous measuring process is not possible thereby. 
         [0006]    Measuring apparatuses are often used for continuous measuring which take volumetric measurements of the fuel flow. The used-up fuel mass is determined therein by means of an additional density measurement which represents the actually required quantity to be measured. Direct measurement of mass consumption, which avoids the disadvantage of an additional density measurement, can be presently realized only intermittently through the weighing method and continuously with Coriolis sensors. 
         [0007]    Modern internal combustion engines require for proper operation defined and flow-dependent pressure conditions mostly in the fuel delivery line as well as in the possibly existing fuel return line. 
         [0008]    According to the Austrian Utility Model No. 3,350, there is provided a pressure stabilization device for stabilization of the initial pressure of the mass flow sensor to be able to create the required low and constant pressure at the connection point to the consumer (generally a few millibars). In fact, the flow-dependent pressure drop at the mass flow sensor must be variably compensated (up to 2 bars, for example). In particular, highly frequent, erratic or pulse-like drawing of fluid must be quickly taken into consideration. 
         [0009]    In the above-mentioned continuous method of fuel measuring, a pressure regulator is attached upstream from the actual flow sensor for pressure stabilization whereby the pressure regulator adjusts the flow-dependent pressure at the output of the measuring system to a constant exit pressure. The disadvantage of such a design is that conventional mechanical pressure regulators act like a “hydraulic diode,” which is to say that the flowing medium can flow through the regulator only in one direction, namely downstream. A measuring system designed with such a pressure regulator does not represent an open system. Should fuel have to be returned from the injection system into the measuring system—or should there occur thermal expansion of fuel through the increase in temperature by a consumer that has stopped running—then there develops often an inadmissibly high pressure increase in the fuel system, depending on the elasticity of the lines, which stresses the lines and the built-in devices and which must be compensated possibly by costly pressure compensating devices. 
         [0010]    It was the object of the present invention to provide a method and a device that ensures continuous, accurate, timely and highly discriminating consumption measuring with regulated exit pressure for the fluid, and which permits a return flow of at least short duration and also temperature-related expansion of the fluid. 
       SUMMARY OF THE INVENTION 
       [0011]    The inventive method is characterized for the achievement of this object in that it includes the steps of measuring the fluid flow with a continuously-operating flow sensor with variable pressure drop, adjusting the pressure downstream of the flow sensor to a constant value by means of a pressure regulator, and upon exceeding a discretionary pressure level downstream of the pressure regulator, guiding fluid back into the pressure regulator from downstream of the pressure regulator in an amount that corresponds to the volume causing said exceeding said discretionary pressure level. This allows that fluid is fed into the pressure regulator upon exceeding a discretionary pressure level. The return flow or the volume change of the fluid to be measured can be compensated thereby without a large effort in terms of equipment and technological methods. 
         [0012]    According to an advantageous embodiment example of the invention, the pressure caused by the excess fluid guided back into the pressure regulator lifts an element acting upon the valve element from the valve element by an amount exceeding the amount necessary for the pressure regulating function. Consequently, a volume of fluid can be fed into the pressure regulator which corresponds to the volume causing the increase in pressure. It is ensured thereby that the measurement results are not influenced since the exact volume captured in the pressure reservoir has already passed the flow sensor. 
         [0013]    To protect the system against any danger of damage through undue pressure increase, it is advantageously proposed according to the invention that an additional volume of fluid exceeding the maximum volume that can be moved into the pressure regulator, creating pressure increase, is diverted. 
         [0014]    The pressure regulator described above is inventively characterized for achievement of the object above in that it includes a housing which includes an upper housing part and a lower housing part, the upper and lower housing parts defining an internal chamber therebetween, the lower housing part furthermore defining an inlet channel, an outlet channel and a valve channel therebetween, and a flexible diaphragm mounted inside the housing for dividing the internal chamber into a variable volume upper chamber an a variable volume lower chamber. The flexible diaphragm biases a movable valve element to open the valve channel when the flexible diaphragm moves downwardly to enlarge the upper chamber and shrink the lower chamber, and to close the valve channel when the flexible diaphragm moves upwardly to shrink the upper chamber and to enlarge the lower chamber. First biasing means are used for biasing the valve element to close the valve channel when the flexible diaphragm moves upwardly and second biasing means are used for biasing the valve element to open the valve channel when the flexible diaphragm moves downwardly, and a bore in the lower housing part connects the outlet channel with the lower chamber, such that a back flow of pressurized fluid medium into the outlet channel will flow through said bore into said lower chamber to move the flexible diaphragm upwardly to close the valve channel, the flexible diaphragm being upwardly flexible after the valve element closes the valve channel to provide a compensating volume for storage of back flowing pressurized fluid medium. The second biasing means is constituted by at least an elastic element acting upon the flexible diaphragm, and the upper housing part is free of stop structures and the flexible diaphragm can be deflected into the upper housing part to compress the elastic element more than necessary to close the valve channel by means of the valve element, thereby enlargening the lower chamber to define a catch volume for the pressurized fluid medium that flows back into the pressure regulator. The already necessary pressure regulator is used at the same time as a compensating vessel along with the advantage of the simple design of the system and a system that can also be retrofitted in a simple manner. The temporarily pushed-back volume or the volume enlarged by temperature-related expansion was already considered in the flow measurement based on the arrangement of the pressure regulator with its compensating volume being behind the flow sensor. 
         [0015]    The compensating volume in the pressure regulator can be formed in a structurally simple manner and in a way that does not negatively influence the function of the pressure regulator in that the pressure regulator is provided with a diaphragm that exhibits a deflection capability of more than 0.03 inches, preferably a deflection capability of more than 0.2 inches. 
         [0016]    Of course, the catch volume is biased by an elastic element, preferably a compression spring. In case of the concave diaphragm, the pressure-regulator spring also takes care of emptying the compensating volume as soon as the pressure diminishes or as soon as the volume becomes smaller or is moved by suction by the consumer. 
         [0017]    The effect of the change of the spring constant at larger deflections can be taken into account in an embodiment of the invention in which said upper housing part defines an inlet bore for delivering compressed fluid medium into said variable volume upper chamber and an outlet bore for removing said fluid medium from said upper chamber, said fluid medium in said upper chamber additionally biasing said valve element via said flexible diaphragm. Thus, the effect of the elastic element can be supported or even overridden by, e.g., compressed air having a controllable pressure and biasing the catch volume. 
         [0018]    According to an additional characteristic of the invention, a safety valve can be provided downstream from the sealing element of the pressure regulator whereby it is ensured that no inadmissible or dangerous pressures can appear even at a pressure increase that may deviate to be higher than in normal operation or at an increase of volume exceeding normal operation. 
         [0019]    If in an advantageous embodiment of the pressure regulator, the safety valve is closed by a sealing element, which is biased in the closing direction with compressed air at the same pressure as the one in the catch volume, then automatic adjustment of the safety valve relative to the set system pressure occurs, which means, secure locking in the closed position of the valve in the range of the normally adjustable volume changes. 
         [0020]    According to an advantageous embodiment of the invention, the compressed air connection to the safety valve can be blocked by means of a sealing element connected to the concave diaphragm to achieve automatically a freeing of the safety valve in a simple and operationally safe manner. 
         [0021]    The above-described pressure regulator is advantageously and preferably used in an inventive device for continuous measuring of dynamic fluid consumption, particularly of fuel. 
         [0022]    The invention will be described in more detail in the following description with the aid of an embodiment example and in reference to the accompanying drawings. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS  
         [0023]      FIG. 1  depicts a schematic diagram of a system for continuous measuring of fuel consumption, 
           [0024]      FIG. 2  shows a pressure regulator according to the state-of-the-art in a sectional view, 
           [0025]      FIG. 3  shows a sectional view of a pressure regulator according to a first embodiment of the invention, and 
           [0026]      FIG. 4  shows a sectional view of a pressure regulator according to a further embodiment of the invention. 
       
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
       [0027]    A tank  2 , being a reservoir, is supplied with fluid , namely fuel, through a line A and a preferably electro-magnetically operable fill valve  1 . The tank  2  is further provided with a float switch or overflow  3 , a fuel level sensor  4 , as well as a preferably manually operable drain valve  5 . 
         [0028]    Fuel is delivered from the tank  2  by means of a preferably adjustable fuel pump  6  via a line B to the continuously operating flow sensor  7 , preferably a Coriolis sensor. The fuel subsequently reaches the delivery point via an electro-pneumatically operable shut-off valve  8  in line B onto which the engine is connected as consumer (not illustrated) and on which delivery point the fuel is to be available under a specific preset pressure. 
         [0029]    A pressure regulator  9  is inserted behind the shut-off valve  8 , which adjusts the pressure in line B behind the flow sensor  7  corresponding to an adjustable preset value whereby the pressure is the delivery pressure to the consumer. As it is explained in the following, especially with respect to  FIG. 3 , the pressure regulator  9  is able to take on a specific amount of fluid which is returned by the consumer through line B or it is able to accommodate an increase in volume which is caused by the temperature-related expansion of the fluid in the system. 
         [0030]    An additional line  10  can be advantageously provided between the pressure regulator  9  and the tank  2  whereby the line  10  starts from a possible safety valve on the pressure regulator and which safely carries fuel volumes into the tank  2 , which exceed the volume that can be taken up by the pressure regulator  9 . 
         [0031]    An additional line  11  can branch-off from line B between the pressure regulator  9  and the delivery point to the consumer and it can lead back to the tank  2  as well via an electro-pneumatically switchable venting/bypass valve  12 . 
         [0032]    A venting process inside the device can be realized thereby when the valve  12  is turned on. Provisions for an additional fuel return line E makes venting of the fuel lines possible up to the consumer whereby the fuel return line E ensures a direct connection between a possibly existing return line of the consumer and the tank  2 . 
         [0033]    A traditional pressure regulator, as it was used up to now in systems described above, is illustrated in  FIG. 2  in a sectional view. A diaphragm  23  is clamped between a lower housing  21  and an upper housing  22  whereby the diaphragm  23  acts upon a valve element  25  via a tappet  24  and whereby the valve element  25  is biased by a closing spring  26 . A reinforcement plate  27  abuts the diaphragm  23  whereby the spring  29  is captured in compression between the reinforcement plate  27  and the adjustable support element  28 , and whereby the spring  29  permits adjustment of the desired pressure by means of the adjustment screw  30 . The fluid pressure at the output  32  of the pressure regulator effects, via a boring  33 , the side of the diaphragm  23  disposed opposite of the spring  29 . When the fluid pressure at the output  32  exceeds thereby a value determined by the force of the spring, the diaphragm  23  is lifted from the tappet  24  and the valve element  25  is urged to a closed position by the closing spring  26 . If the pressure decreases, in contrast, then the spring  29  pushes the diaphragm  23  downwardly whereby the valve element  25  is lifted from the seat by the tappet  24 . A connection is thereby also established between the input  34  of the pressure regulator and its output  32  so that fluid can be replenished and increase the pressure at the output-side to such a degree until the diaphragm  23  is pushed up against the force of the spring  29  and until the valve element  25  has reached again the closed position. 
         [0034]    If, however, the pressure becomes too great at the output  32  of the pressure regulator while the valve element  25  is closed—or if the fluid is pushed back into the pressure regulator through the output  32 —then the diaphragm  23  can deflect only to a small degree and the pressure will continuously increase or, otherwise, it must be compensated by additional built-in devices in the system. 
         [0035]    As with any other known pressure regulators, the diaphragm  23  has only a very limited deflectability. The deflectability is only necessary for the pressure regulating function and not for increasing the volume of the inside of the pressure regulator housing  21 ,  22  that is accessible for the fluid to be pressure-regulated. Typical distances for diaphragm deflections in direction to the upper housing  22  are about 0.03 inches. That deflection is not greater than a deflection necessary for acting upon the valve element  25  and after closure of the valve element  25  the diaphragm  23  cannot move upwards any more and can therefore not store more fluid in the volume defined by the diaphragm  23  and the lower housing part  21 . 
         [0036]    In the pressure regulator of the invention illustrated in  FIG. 3 , there is also a diaphragm  40  clamped between a lower housing  41  and an upper housing  42 . This diaphragm  40  is preferably a concave diaphragm, which can be deflected to a great degree compared to a flat diaphragm. That means that the deflection of the diaphragm  40  will exceed about 0.03 inches towards the upper housing  42 . Preferably the deflection of the diaphragm  40  will be more than 0.2 inches. That amount of deflection is considerably greater than a deflection necessary for acting upon the valve element  49  from which the diaphragm  40  is preferably lifted after the valve element  49  has reached its closing position. To allow such deflection the upper housing part  42  is free of all structures that could define a stop for the diaphragm  40 . 
         [0037]    Consequently, a catch volume functionality is provided which is defined by the increased volume under the diaphragm  40 , connected to the outlet port of the pressure regulator. This catch volume can store an amount of fluid usually greater than 10 ml in case of back flow through the output  46  back into the housing  41 ,  42  of the pressure regulator. Such backflow—as occurring for example in case of startup of modern diesel engines (Common Rail)—will give rise to a movement of the diaphragm of usually more than the 0.03 inches that a normal diaphragm can be deflected, usually 0.2 inches or more. By storing this amount of fuel a sudden pressure increase in case of backflow can be omitted. 
         [0038]    A compression spring  59  is interposed between the upper housing part  42  and the diaphragm  40  and biases the diaphragm  40  to move downwardly. Thus, the compression spring  59  is biased a valve element  49  in a valve channel between the input  48  and the output  46  of the pressure regulator to open the valve channel. Thereby, the compression spring  59  defines the closing force of the valve element  49  and as such the pressure level at the output side of the pressure regulator. 
         [0039]    The pressure regulator  9  of the invention operates also like the traditional pressure regulator described above whereby communication between the input  48  and the output  46  is controlled by the valve element  49  dependent on the pressure at the output  46  of the pressure regulator  9 . As in a traditional pressure regulator, the valve element  49  is biased by the closing spring  50  in the closing direction and brought to the open position by means of the compression spring  59  and the diaphragm  40  by means of the tappet  51  when the pressure at the output  46  drops below a value that is defined by the force acting upon the diaphragm  40  from above. 
         [0040]    A safety valve  54  is provided at the side of the output to securely take care of the increased volume or pressure at the output-side of the pressure regulator  9  exceeding the deflection of the concave diaphragm  40 . The valve element  55  of the safety valve  54  is biased by a closing spring  56  and it keeps closed in normal operation the pressure relief passage  57  extending from the output  46  of the pressure regulator. In the embodiment illustrated in  FIG. 3 , the compressed air flowing from the boring  53  in the upper housing is guided to an in-flow boring  58  in the safety valve  54  to securely maintain the closed position at any pressure set at the output-side. Any selected pressure setting that is above the pressure level of the compressed air biasing the diaphragm is automatically forwarded to the safety valve  54  whereby this pressure level effects also the closing element  55  in addition to the force of the closing spring  56 . 
         [0041]    When the compensating volume, which is determined by the deflection of the concave diaphragm  40 , is completely filled, the sealing surface  44  rests against the inner side of the boring  53  by forming a seal at full deflection and prevents the out-flowing of compressed air from the upper housing  42  all the way to the safety valve  54 . The closing element  55  of said safety valve  54  is biased alone by the closing spring  56  and the safety valve  54  can open as soon as the thereby defined maximum pressure has been reached at the output of the pressure regulator  9 . The pressure relief passage  57  is advantageously connected to the tank  2  of the system through line  10  as indicated in  FIG. 1 . 
         [0042]    In the pressure regulator of the invention illustrated in  FIG. 4 , again the diaphragm  40  is clamped between a lower housing  41  and an upper housing  42 . This diaphragm  40 , preferably a concave diaphragm as the one in  FIG. 3 , can be deflected to the sum of distances P and C, which is a considerably greater degree compared to a flat diaphragm with maximum deflection P. 
         [0043]    Deflection P is the amount necessary for the pressure regulator functionality, i.e., the deflection—about 0.03 inches in direction to the upper housing  42 —necessary for acting upon the valve element  49  to move it between its opening and closing position, respectively. 
         [0044]    After having been deflected by amount P and having brought the valve element  49  in closing position, and if the pressure rises on the outlet side of the pressure regulator, the diaphragm  40  can be lifted from the valve element  49  or from tappet  51  and can be further deflected to amount C. While the deflection P only results in a very small volume VP (appx. the area of the diaphragm  40  multiplied with the deflection P), the greater deflection capability C—considerably exceeding said about 0.03 inches and preferably more than 0.2 inches—provides for a huge catch volume VP and VC under the diaphragm  40 . Within the catch volume VP and VC, usually greater than 10 ml, all fluid can be stored that causes a rise in pressure at the outlet side and/or that flows back through the output  46  into the housing  41 ,  42  of the pressure regulator. Consequently, a more or less sudden pressure increase in case of backflow can be omitted. 
         [0045]    As is understood, the principles explained in connection with  FIG. 4  also apply to all embodiments of the present invention, in particular to those with any kind of compression springs for biasing the diaphragm  40 , as shown in  FIG. 3 . 
         [0046]    When present, a sealing element  43  connected to the diaphragm  40  makes contact with the upper side of the upper housing  42 , too. The sealing element  43  is preferably attached with its sealing surface  44  on the upper one of the two reinforcement plates  45 . A considerable volume of fuel can be accommodated in the housing of the pressure regulator  9  through the deflection of the concave diaphragm  40  whereby the volume can be pushed back through the output  46  and the boring  47  under the diaphragm  40 . 
         [0047]    The force onto the diaphragm  40  can be generated by means of an adjustment spring  59 , as in the case of traditional pressure regulators. However, the force can also be produced, even in addition to the compression spring  59 , by means of compressed air, independent from any deflection, and which preferably flows continuously through the boring  52  into the upper housing  52  and flows out again through the boring  53 .