Abstract:
A flowmeter capable of real-time fuel mass flow measurement involving extremely low fuel mass flow quanta. The flowmeter includes a dual flow path conduit system, a flow control for alternating the selection of one flow path exclusive of the other flow path, an indicator tube interfaced with the conduit system, an indicator shuttle slidably mounted in the indicator tube, and a sensor for sensing the position of the indicator shuttle relative thereto.

Description:
TECHNICAL FIELD  
         [0001]    The present invention relates to flowmeters for measuring the mass per unit time of flow of a liquid. More particularly, the present invention is a flowmeter for measuring a quantized mass of fuel flow. Still more particularly, the present invention is a flowmeter of the aforesaid type capable of measuring extremely small fuel mass flow quanta.  
         BACKGROUND OF THE INVENTION  
         [0002]    The ever increasing sophistication of control of the various processes of internal combustion engines has provided increased mileage, decreased emissions and better overall performance. These advances include the widespread use of electronic controls and fuel injection. Fuel injectors, controlled electronically, provide precise, timed fuel injections directly into the combustion chamber at the most opportune portion of the engine cycle. One of the remaining issues of engine control relates to knowing the real-time quantized fuel flow mass delivered to a combustion chamber by its respective fuel injector.  
           [0003]    Fuel flows, on a cycle resolved or on a per injection basis, have been difficult, if not impossible to quantify using conventional mass flowmeters. Therefore, a new style of mass flow meter is required to quantify small flows (mass quanta) accurately to within 0.1 mg per injection. The need for this type of higher accuracy device is to make better mass specific emission measurements. Fast low flow exhaust devices exist for cycle resolved emissions but no information is available for cycle resolved input of the reactants. Further, most other flowmeters do not operate at the high pressures required for direct injection internal combustion engines.  
           [0004]    Accordingly what remains needed in the art is a flowmeter capable of measuring extremely small fuel mass flow quanta in real-time.  
         SUMMARY OF THE INVENTION  
         [0005]    The present invention is a flowmeter capable of real-time fuel mass flow measurement involving extremely low fuel mass flow quanta.  
           [0006]    The flowmeter according to the present invention includes a dual flow path conduit system, a flow control for alternating the selection of one flow path exclusive of the other flow path, an indicator tube interfaced with the conduit system, an indicator shuttle slidably mounted in the indicator tube, and a sensor for sensing the position of the indicator shuttle relative thereto.  
           [0007]    In operation, one flow path is first selected, whereupon a first quantum of fuel mass flows down the first selected flow path, causing the indicator shuttle to be displaced in a first direction along the indicator tube an amount related to the volume of the first quantum of fuel mass flow. This first displacement is registered by the sensor, for example optically via change in area of indicator shuttle occlusion of a photo-sensor with respect to a laser source, and is then output to an electronic circuit. Next, the other path is secondly selected, whereupon a second quantum of fuel mass flows down the second selected flow path, causing the indicator shuttle to be displaced in a second direction (opposite to the first direction) along the indicator tube an amount related to the volume of the second quantum of fuel mass flow. This second displacement is also registered by the sensor, again for example optically via change in area of indicator shuttle occlusion of a photo-sensor with respect to a laser source, and is then output to the electronic circuit. A simple algorithm of the electronic circuit calculates the fuel mass flow of each sensor output. This real-time generated fuel mass flow data is then, for example, used by the engine control module to adjust engine operational parameters pursuant to programming.  
           [0008]    Accordingly, it is an object of the present invention to provide a flowmeter having the capability of measuring in real-time extremely low fuel mass flow quanta.  
           [0009]    This and additional objects, features and advantages of the present invention will become clearer from the following specification of a preferred embodiment. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0010]    [0010]FIG. 1 is a side view of a the flowmeter according to the present invention, shown in operation with respect to a fuel injector.  
         [0011]    [0011]FIG. 2 is a partly sectional side view of the flowmeter according to the present invention, shown at the end of a first quantum of fuel mass flow along a first flow path.  
         [0012]    [0012]FIG. 3 is a sectional view, seen along line  3 A- 3 A of FIG. 2.  
         [0013]    [0013]FIG. 3B is a sectional view, seen along line  3 B- 3 B of FIG. 2.  
         [0014]    [0014]FIG. 4 is a partly sectional side view of the flowmeter according to the present invention, shown at the end of a second quantum of fuel mass flow along a second flow path.  
         [0015]    [0015]FIG. 5A is a plan view of a sensor surface, showing occlusion area with respect to the indicator shuttle at the relative position shown at FIG. 2.  
         [0016]    [0016]FIG. 5B is a plan view of the sensor surface, showing occlusion area with respect to the indicator shuttle at the relative position shown at FIG. 4. 
     
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT  
       [0017]    Referring now to the Drawing, FIG. 1 depicts an environment of operation of the flowmeter  10  according to the present invention. The flowmeter  10  is located between a source of pressurized fuel  12  and a fuel injector  14 . An electronic control module  16  is connected to an external circuit  18 , wherein electronic components of the flowmeter (discussed hereinbelow) are operably interfaced. Pressurized fuel F (as for example between 1,000 and 5,000 psi) is delivered to the fuel injector  14  by the pressurized fuel source  12 , wherein the fuel passes through the flowmeter  10 . The flow of fuel is quantized, in that an injection is timed pursuant to programming of an engine control module which regulates the injection function of the fuel injector.  
         [0018]    The primary intent of the present invention is it to provide direct fuel mass flow measurements on an actual pressurized fuel line proximal the fuel injector, wherein data is realized on a cycle-by-cycle basis, and wherein it is preferred for the flowmeter to have sufficient hydraulic damping and fast enough signal response time for providing real-time data output on an intracycle basis. The sensor output of the flowmeter is converted electronically by an algorithm to mass flow data. The secondary intent of the present invention is to keep the size of the flowmeter small enough to enable the installation under the hood of test vehicles.  
         [0019]    Referring now additionally to FIGS. 2 through 5B, the structure and function of the present invention will be detailed.  
         [0020]    An input fuel line  12   a  from the source of pressurized fuel  12  communicates with an input port  20  of the flowmeter  10 . The input port  20  communicates with a 3-way digital hydraulic valve  22  having an input  24 , a first output  26  and a second output  28 . Selection of which of the first and second outputs  26 ,  28  are flowably operative relative to the input  24  is responsive to digital electronic signals from the electronic control module  16 . An example of a suitable 3-way digital hydraulic valve is manufactured by Sturman Industries of Colo. Springs, Colo., having an advertised switch time of under 1 millisecond.  
         [0021]    Connected to the first output  26  is a first conduit  30 , and connected to the second output  28  is a second conduit  32 . The first and second conduits  30 ,  32  are formed in a meter body  34  which may be composed of any durable, rigid material which is suitable for a pressurized fuel environment. For ease of fabrication the meter body  34  may be composed of four separate body members  34   a ,  34   b ,  34   c ,  34   d  mutually joined in a leak-proof manner by any suitable connection modality. The meter body  34  is configured so as to provide an interior space  36 .  
         [0022]    An indicator tube  38  is placed in the interior space  36 , wherein each end of the indicator tube is joined, respectively, in a communicating manner with the first and second conduits  30 ,  32 . In this regard, the indicator tube  38  is rigidly affixed to the meter body  34  during assembly of the meter body, and a leak-proof seal is provided between the ends of the indicator tube  38  and the first and second conduits  30 ,  32 . The preferred indicator tube  38  is optically clear, having an index of refraction equal to that of the fuel F. It is additionally preferred for the indicator tube to be composed of quartz or a pyrex glass, either of which having a polished sidewall of the passageway  38   a  thereof. The indicator tube  38  may be provided, for example, by drilling a block of quartz, or other suitable fabrication technique. The exterior shape and the shape of the passageway  38   a  may or may not be cylindrical.  
         [0023]    Located within the passageway  38   a  of the indicator tube  38  is an indicator shuttle  40 . The sidewall  40   a  of the indicator shuttle  40  is also polished, and is dimensioned to complementarily fit the shape of the passageway  38   a , wherein there is a slip-fit therebetween such that the shuttle is easily slidable along the inside of the passageway. The slip-fit may be, for example, assured by a verification test in which a dry slip-fit is observed prior to final assembly. By way of example, a clearance between the sidewall  40   a  of the shuttle  40  and the sidewall  38   a  of the passageway  38  may be on the order of about 0.002 inches. The indicator shuttle  40  is composed of a material which is incompressible and matches the density of the fuel F.  
         [0024]    Each of the first and second conduits  30 ,  32  terminate, respectively, at a second 3-way digital hydraulic valve  42  having a first input  44  connected to the first conduit, a second input  46  connected to the second conduit, and an output  48  connected to an output port  50 . An output fuel line  14   a  connects to the fuel injector  14  and communicates with the output port  50 . The second 3-way hydraulic valve  42  is preferably identical to the first 3-way digital hydraulic valve and operates as mentioned with respect thereto (in a reverse fuel flow operational sense).  
         [0025]    A position sensor  54  is located in the interior space  36 , which senses the position of the indicator shuttle  40  relative thereto. The position sensor may be any sensor which senses position of the indicator shuttle  40  relative to the indicator tube  38 , for example via a magnetic, optic or sonic sensor. The preferred position sensor is an optical sensor having an emitter component  56  and a receiver component  58 . The preferred emitter component  56  is a laser which is powered and controlled, for example, via the electrical circuit  18  and the electronic control module  16 . The preferred receiver component  58  is a photo sensor which is sensitive to the light emitted by the laser, and provides a signal output to the electronic control module  16  responsive to the area of the beam  60  which falls upon the photo-sensitive reception area  66  of the receiver component. An example of a suitable position sensor  54  in the form of a laser and photo sensor is available through LMI Technologies, Southfield, Mich., which is advertised to have an analog output at speeds up to 10 kHz, and have an accuracy to within 1 part in 1,000.  
         [0026]    With respect to operation of the indicator shuttle  40  vis-a-vis the position sensor  54 , the indicator shuttle is opaque, preferably fully opaque, to the light emitted by the emitter so that an end portion  40   p  of the indicator shuttle  40  occludes the beam  60  (see FIGS. 2 and 4). In this regard, the light occluding properties of the indicator shuttle  40  is such that it casts a shadow of the beam  60  from the emitter component  56  upon the reception area  66  of the receiver component  58 , as shown at FIGS. 2 and 4.  
         [0027]    For example, FIG. 5A shows the reception area  66  when the indicator shuttle  40  is at the position shown at FIG. 2. In this case, the beam  60  is occluded by only a small end portion  40   p  of the indicator shuttle  40 , so that there is a large area  64  where the beam strikes upon the reception area, and but a small area  68  where the beam does not strike upon the reception area. For example further, FIG. 5B shows the reception area  66  when the indicator shuttle  40  is at the position shown at FIG. 4. In this case, the beam  60  is occluded by a large end portion  40   p ′ of the indicator shuttle  40 , so that there is but a small area  64 ′ where the beam strikes upon the reception area, and a large area  68 ′ where the beam does not strike upon the reception area. The signal output of the receiver component  58  is related to how much of the beam is occluded by the indicator shuttle.  
         [0028]    A predetermined maximum reciprocable displacement of the indicator shuttle  40  along the indicator tube  38  is defined to be within a reception length L of the beam  60  (unshielded) falling upon the reception area  66  which is parallel to the detection axis A of the reception area (see FIG. 4, where it is shown that the detection axis is parallel to the centerline of the passageway  38   a ). Therefore, the maximum reciprocable displacement D of the indicator shuttle  40  must be smaller than the reception length L. For example, given a 24 mm long sensor reception length along the detection axis, indicator shuttle reversal is necessary before the indicator shuttle edge  40   e  of the indicator shuttle  40  reaches the ends of the reception length (that is, the maximum reciprocable displacement of the indicator shuttle is under 24 mm). In this example of a 24 mm reception length, the position sensor  54  can resolve indicator shuttle displacements of 0.001 inches at high speed relative to a 100 Hz maximum fuel injection frequency. The output from the receiver component  58  provides an absolute indication of position of the indicator shuttle edge  40   e  of the indicator shuttle  40  based upon the shadow cast on the reception area  66 , wherein a voltage output is related to the area of the shadow cast, for example between 0 and 10 volts.  
         [0029]    In operation, an engine control module periodically commands a fuel injector  14  to inject a quantity of fuel into a combustion chamber. Between these commands, the electronic control module  16  commands the two 3-way valves  22 ,  42  to switch the flow paths. The first flow path P, shown at FIG. 2, has a first segment along the first conduit  30  (due to the first output  26  being open and the second output  28  being closed), a second segment along the indicator tube  38  in a first direction, and a third segment along the second conduit  32  (due to the second input  46  being open and the first output  44  being closed). The second flow path P′, shown at FIG. 4, has a first segment along the second conduit  32  (due to the second output  28  being open and the first output  26  being closed), a second segment along the indicator tube  38  in a second direction that is opposite the first direction, and a third segment along the first conduit  30  (due to the first input  44  being open and the second output  46  being closed). Each fuel injection delivers a unique quantum of fuel to the fuel injector, wherein the indicator shuttle  40  shuttles back and forth (reciprocates) an amount related to the volume of each injection. The amount of the beam  60  occluded by the indicator shuttle as a result of each injection is dependent upon the position of the indicator shuttle edge  40   e  at the end of each injection. The amount of occlusion of the beam  60  directly relates to the signal output produced by the receiver component  58 . The signal output is sent to the electronic control module  16 , which then outputs a signal to the external circuit  18  which is interfaced, for example, with the engine control module.  
         [0030]    With the foregoing details recounted, it is instructive to further consider the following commentaries regarding implementation of the flowmeter  10 .  
         [0031]    A primary feature of the flowmeter  10  is an indicator tube having an index of refraction equal to that of the liquid, and a light shielding indicator shuttle having a density equal to that of the liquid. These features provide a non-contact high accuracy method of resolving displacement of the indicator shuttle in response to quantized fuel mass flow. In this regard, the indicator shuttle will move nearly instantaneously with the liquid flow. In comparison with other high pressure devices for flow measurement, there is seen sealing and pulsation difficulty. With the flowmeter  10 , leakage and internal drag are minimized.  
         [0032]    The position sensor may utilize any suitable frequency of electromagnetic radiation (as for example optical, ultraviolet, or microwave frequencies), and, alternatively, may be other than electromagnetic radiation based, as for example it may operate on a sonic basis, wherein the indicator shuttle is phonon shielding. Alternatively further, the indicator shuttle may be magnetic and the position sensor may be a magnetometer. An optical embodiment of the position sensor would use a laser LED or other such commercial collimated light source and an optical receiver sensor to count pulses or the displacement of the reciprocably moving indicator shuttle. By comparison, other meters rely on rotating mechanical parts with seals and possible leaks. They use exotic pressure compensation schemes to balance pressures that cause inaccuracy, and do not tolerate accoustic wave pulses and pressure fluctuations. The flowmeter  10  tolerates pulses; it is designed to measure them.  
         [0033]    The flowmenter  10  should have the capability of resolving directional ambiguity and correcting for it. In this regard, the position sensor is connected to a signal conditioner and/or an electronic control module (computer controller). Thus, forward and reverse pulses can be resolved and accounted for. The reception area may be a line of photodiodes or other such light absorbing device to sense the absolute position of the edge of the indicator shuttle may be used to determine the indicator shuttle displacement.  
         [0034]    The diameter of the indicator tube and the displacement of the indicator shuttle comprise a direct volume measurement at a measurement chamber  38   c . By using small diameter indicator tubes of between 2 to 3 mm inside diameter, fuel flows as low as 0.1 milligrams per pulse should be possible, wherein the position sensor sends signals related thereto to the electronic control module. The electronic control module (or signal conditioning module) then uses the temperature, specific gravity, and density information which is characteristic of the fuel to calculate fuel mass per injection event. The flowmeter  10  resolves the time history of discrete injection events as they happen, and does not integrate over thousands of cycles for an average. The known diameter of the indicator tube and the certainty of the indicator shuttle displacement provide absolute accuracy of the signal output.  
         [0035]    The operational methodology of the flowmeter  10  is a reversing indicator shuttle displacement, a likeness to a reversing spool type hydraulic valve of an “H” bridge. Several types of suitable electro and/or servo hydraulic 3-way valves are available on the market.  
         [0036]    Unlike most other fuel meters the flowmeter  10  operates at injection pressure. Further, it is mounted directly or in close proximity to the fuel injector. By comparison, other meters are housed in cabinets several feet or yards from the engine. The reduction of fuel volume within the system increases accuracy. By having a small flowmeter operating at high pressure close to the fuel injector, vapor introduced from excess plumbing and pumps is negligible. This further simplifies the metering system and reduces size and the contained volume within the measuring chamber  38   c.    
         [0037]    The flowmeter  10  is a small, compact device which can also be used for a variety of liquids, besides fuels; and can also be used for many applications, automotive and other than automotive. With regard to automotive applications, the flowmeter  10  can be used with a wide variety of fuels, vehicles, farm implements, motorcycles, marine, and may include small injected engines, direct and port fueled, of displacements less than 50 cc.  
         [0038]    The flowmeter  10  is easily adapatable to differing measuring environments. Typically, all that is needed is changing the indicator tube and the indicator shuttle, while the valving, electronics, position sensor and meter body remain unchanged. For example, single cylinder engines of 500 cc would require a 3 mm internal diameter indicator tube and matching indicator shuttle. Larger engines could use a 5 mm or greater internal diameter indicator tube with matching indicator shuttle. This feature builds in flexibility while reducing cost and complexity.  
         [0039]    Any transparent liquid can be used. Both gasoline and diesel fuel will work nicely. Low pressure fuel systems can be used as well. Any pulsed per cycle injector can be metered on a cyclical basis. The key is in matching the density of the liquid to the density of the indicator shuttle. This matching of density provides simultaneous movement of the indicator shuttle with the movement of the adjacent columns of fuel (at either end of the indicator shuttle). The fuel and the indicator shuttle are inside the indicator tube, which is a drilled and polished quartz (pyrex, etc.) block or tube.  
         [0040]    Care must be taken to allow a slip-fit between the indicator tube and the indicator shuttle. The issues associated with sidewall interaction vis-avis the passageway and the indicator shuttle, internal leaking past indicator shuttle, fast reset, and hydraulic disturbances to the injector are the major concerns. The sidewall interaction will be addressed by a verified dry slip fit at assembly, wherein polishing and a suitable diametric clearance (by way of mere non-limiting example, on the order of about 0.002″) should be sufficient. Clearance and density matching will minimize internal leakage past the indicator shuttle, wherein the indicator shuttle should move as if it were the fuel itself. With negligible pressure differential, the clearance should not leak. The 3-way valves should introduce no volume differential to the system as they move. They also move a short distance in very short times, so there should be no hydraulic force applied internal or external to the system. Accordingly, introduced resonance and ringing should be minimized. With regard to the effect of the flowmeter  10  on fuel injector performance, experiments on fuel injectors at 10 Mpa have shown that the fulel injector itself is a major contributor to system perturbations. The flowmeter  10  may need damping to deal with fuel injector step function like behavior.  
         [0041]    To those skilled in the art to which this invention appertains, the above described preferred embodiment may be subject to change or modification. Such change or modification can be carried out without departing from the scope of the invention, which is intended to be limited only by the scope of the appended claims.